How To Solve Amazon's Hanging Cable Interview Question

[@MindYourDecisions]

I don't want to sound hyperbolic, but this problem is actually a "cinch" if you think about it. Thanks for 5 million views in 1 year! (Perhaps the most watched math video of the last 12 months on KZbin, you guys are awesome!)

[@icarovidalfreire2209]

Some doubts *(1)* If the lowest part of the cable is 20m, the catenary equation is y (x) = 20.cosh (x / 20). Hence, as y (x) = 50, we have 20.cosh (x / 20) = 50, ie x = 20.acosh (5/2), or rather x is approximately 31.33m. Therefore, the distance between the posts is 62.66m. Furthermore, using the arc length formula, we arrive at half the length of this catenary at L = 20 senh (31.33 / 20), ie approximately L = 45.81m. What would give as total length of the catania: 91.62m. In short: if the shortest distance from the wire to the ground is 20m and the wire describes a fixed catenary on the 50m poles, the length of this cateraria is NOT 80m but 91.62m. *(2)* Assuming the length of the wire is 80m, and we do not know the parameter "a" ... Then, using the arc length in half of the catenary, we find senh (x / a) = 40 / a. And, since y (x) = 50, we would have "a" . cosh (x / a) = 50, hence cosh (x / a) = 50 / a. Using the fundamental relation we find (50 / a) ^ 2- (40 / a) ^ 2 = 1. Hence, a = 30. Using this value, we deduce that cosh (x / 30) = 50/30, ie x = 30 *.acosh (5/3), or approximately x = 32.96m. Hence, the distance between the posts would be 65.92m. In short: if the wire length is 80m, the shortest distance from the wire to the ground cannot be 20m. It should be 30m. Where am i going wrong? Note: Sorry for my English. =)

[@thefirminator]

@@icarovidalfreire2209 ya know i didn't understand anything but ig u r right

[@icarovidalfreire2209]

@@thefirminator Didn't you understand because of my english or why there are any errors in my calculations? 😅😂

[@it8755]

Whether we could not consider the line as parabola

[@multiversegamer13]

Psychopath

[@barberbill63]

The official answer to the question is, "Dude, I'm here fore the box folding job. You got me confused with the cable hanging guy."

[@6Sisu9]

W Mcg lol

[@MP-ym8lg]

Lmao

[@wiliambanquiter8039]

W Mcg 👏👏👏👏🍾🍻 Youre fuckin hired bruh

[@syr72]

Lmao

[@neilonell6362]

Hahaha

[@MrFrankfurt13]

The actual answer was, "I would measure the distance using a tape measure I bought on Amazon."

[@factswithsatish]

Answer is 30 meters bro

[@ashemoski]

@@factswithsatish - I think you missed the joke, bro.

[@heeyaArtworld]

Same would i do

[@bngr_bngr]

A Fluke laser distance meter is the most accurate.

[@ocalavictory3728]

You're hired, sir.

[@hootinouts]

I am a mechanical designer of 0ver 30 years, been to lots of job interviews, and was hired by many different companies, and I never once encountered any problem like this in any of my interviews. That Amazon would use such a problem in an interview seems totally absurd. Does Amazon hire overhead power transmission line engineers?

[@Snoop_Dugg]

@@abcxyz2927 No these are for the programmers and software developers I would imagine.

[@flackstar007]

My question is if Amazon even pay the people it hires after this level of interviewing questioning anywhere close to what they are worth?

[@Llortnerof]

@@smasherblues5322 50 meters from the ground, 0.5mm tall. Also, they're actually airhooks, not poles.

[@peterwilson8039]

This is like the Google aptitude test that came out ten or fifteen years ago. It's basically an IQ question. Amazon wants to hire smart people.

[@jeremyponcy7311]

The answer is unbelievably simple. No math required. (Hint: the picture is misleading you. Ignore the picture and simply consider the values.)

[@elegy8187]

I think part (b) is a clever interview question, as it requires some outside the box thinking, but part (a) doesn't seem very practical unless they expect you to only approximate the answer. I doubt that most mathematicians know the equation for a catenary from memory. To be honest if given this question I would probably just approximate the cable with a parabola and hope that the answer is close enough.

[@bibliophile4292]

I sort of just solved part (b) by looking at the thumbnail and i was like - wait a second! it's 0 meters

[@NotMyActualName_]

honestly you can even just approximate it with triangles and that's pretty close. All you need is the pythagorean theorum. That gets you to 26.46, which I would probably round up to 27 since we know there's bend in it that will make it longer than a straight line. And if you do this with the second one you'll get the correct answer of 0.

[@HuffyT266]

@@NotMyActualName_ that's exactly how I tackled the problem, but keep in mind that you would actually want to round the number *down* for this scenario! Since the straight line would reach further, compared to a curved line of the same length, the maximum distance decreases as you increase the curvature. I think using the Pythagorean theorem for a quick "off the top of your head" reply (acknowledging that it's only an approximation) is a better alternative, as long as you later can refer to Google and other sources to solve this with the proper equations (which I could never remember by heart, and even if I did, I should not trust that blindly, and would have to double check with trusted sources anyway before taking any kind of important decision). It still is a cool math problem though!

[@sergeyborja]

@@bibliophile4292 i think that the picture was misleading) it is better only to read the task

[@ThomasSorensen1]

I looked at it for a bit a figured I could get close enough with C²-A²=B² and ignoring the tangent might be fine. So I figured A=Height from top of pole to center cable B=Half distance between poles C=Half cable length. I got A²=1600 & C²=1600 and then when, wait - what? Distance between poles is 0? I better finish this video. Then there were all these crazy formulas & I was like damn I must have really messed something up in my reasoning but in the end for 10m version my 30sec solution actually was right. But for 20ft height I would've said 50ft apart and been off by 4.6ft

[@kaianders8773]

I want to meet the people who got this question right during the interview and still ended up working for Amazon.

[@henrymiller4136]

Hi

[@ss0175]

@@henrymiller4136 lmfao

[@ko-Daegu]

You don’t have to Ans to get a job btw Depends if they found what they are looking for you are hired (not vise versa even if you Ans ?

[@juyifan7933]

Lol, this is not an interview for a dead end job. These people were not interviewing to deliver boxes. This kind of problem is asked in tech interviews, so it would be for software engineers, data scientists or mathematicians. They are for jobs that pay over 100k a year as initial salary. The selection process is usually composed of several interviews. These are not the "talk to someone in HR" interviews. They usually consist on problems designed to test the technical skills of the participants. This kind of interview process is standard in big tech companies, google, apple, facebook, amazon...all the big tech companies follow this type of process.

[@____-gy5mq]

Pretty sure this question is for designers/mechanical engineers and not software engineers.

[@colinclarke4285]

This is how Amazon delivery drivers work out how to throw your package over your back garden

[@lilijane46]

😂

[@guepardiez]

That would be a parabola, though. Not a catenary.

[@calebbyers]

This is way underrated.

[@papapetad]

@@guepardiez Not at all. It is called dropping things from a height of 40 meters.

[@paulj8726]

🤣🤣🤣

[@jgunther3398]

When I got a job at Amazon all I had to do was say I could lift 30 lbs.

[@ModernGolfer]

But, how do you KNOW the 2 poles only weigh 30lbs? ;-)

[@lukasmakarios4998]

j miller- 60 lbs

[@zuriel13g]

50 lbs

[@jgunther3398]

Any lifting over 30 is assisted by special device invented by autistics

[@tubular618]

Now they just test how long you can go without using the bathroom.

[@hasantao]

In the interview, I would say we approximate the cable with a line and take x = SQRT(1600 -900) = 26.45. We then multiply by 2. You can also easily see that the second one will be infeasible because it gives us zero distance.

[@williamsorensen3958]

Wait why 1600 and 900?

[@dontreadthis100]

@@williamsorensen3958 Pythagoras theorem, both sides ^2

[@andriyOshtuk]

It is rather x = SQRT(1600 + 900) = 50 and multiply by 2

[@dontreadthis100]

@@andriyOshtuk ???

[@rinckeric4741]

give zero more distance?so you caculation is more correct??

[@lofnouk]

Sounds similar to the question they gave me; "if the bottle we need you to piss into is in the passenger footwell and you are strapped into the driver's seat of a standard delivery vehicle, at what angle of inclination do you need to aim to manage to get most of it into the bottle?"

[@Evilthx]

7 degrees my friend. Unless it is greater than a 16oz bottle.

[@ThatLegendary]

@@Evilthx Fahrenheit or Celsius?

[@Kingkhan-og8xw]

@@ThatLegendary Kelvin My friend

[@ThatLegendary]

@@Kingkhan-og8xw No, my name is Patrick

[@Kingkhan-og8xw]

@@ThatLegendary Nah Kelvin is my friend

[@ColoradoSockies]

As an accountant I would just ask what they want the distance to be.

[@MrVpassenheim]

Ouch!

[@queensgambit4982]

As an accountant I also agree with the other accountant ..

[@WillCarter1976]

As a person who employs an accountant, this is the correct answer.

[@treblesix8730]

Can you do my annual tax return please?

[@SL-nz4hd]

Lol

[@stickyfox]

If you can solve this problem in a few seconds, then they know you're able to deal with a fifteen second bathroom break twice per shift.

[@brentmagazine8496]

Because it only takes 15 seconds to change your diaper.

[@Farrell0208]

That you also have to ask permission to take, right?? Lmao that place is unreal.

[@thesecretkey9845]

Fifteen seconds? What, do you think money grows on trees? Clean your Reusable Amazon Warehouse Employee Diaper (TM) in your washer/dryer when you get home.

[@rebirth_mishap]

You don't have to take bathroom breaks if you don't eat or drink while you're working

[@TheUnfriendlyfire]

Damn you guys have a really bad view of Amazon

[@kanguru_]

For the 10 meter case, if you draw a straight line from the top of one support to the lowest point of the cable, its length has to be less than 40 meters since the cable is a curve. Draw a horizontal line from that lowest point to the same support. Then you have a right angle triangle with a hypotenuse which is less than one of its sides. So the picture, as drawn cannot make sense. The only case which is feasible is when the cable has no curvature, i.e. it is vertical up and down. So the two supports have to be coincident.

[@nighttrain1236]

That sounds like the way to answer the question without pulling out an obscure formula.

[@cookaburra]

@@nighttrain1236 Yes.

[@bramvanduijn8086]

And even then it requires an infinitely thin cable, which means it has zero mass, which, combined with the fact that it has no curvature, means it won't curve as it gets pulled down. The most logical explanation for it having a single lowest point is that the cable is a straight diagonal line to the middle, which means you can use a much simpler formula: you're basically calculating one side of a triangle. For the 10 meter case the answer now is possible, but this also changes the answer for the 20 meter case. We have a triangle with a diagonal side of 40 meters and a vertical side of 30 meters, this gives us a horizontal side of 26.46, for a total distance between poles of 52.9.

[@adityaganjoomech]

I used the exact same approach

[@matthewhall889]

The poles are 12742km apart

[@ObsidianParis]

at one decimal place, they said :-)

[@structlightning]

No its not that much. The answer is near 100

[@rumi9005]

@@FlyFishingChronicles 20,000 km - You're about right, if you're flying. Walking would likely be a bit further (unless you're Jesus of course).

[@paulgoogol2652]

@@rumi9005 I believe you because you said Jesus.

[@rumi9005]

@@paulgoogol2652 - You know my friend Jesús Fuentes? That's quite a coincidence, Paul.

[@eCommKen]

I interviewed people for 6+ years at Amazon. I never once used this type of question. None of my colleagues ever used this type of question. We were never trained to use these types of questions (the training actually encouraged us to dig deep into actual candidate experiences related to the area we were hiring for). Only one time did I ever even hear of someone at Amazon using this type of question in a phone screen, and it struck me as odd because this is not the kind of interviewing Amazon conducts. So PSA: don't assume this is the norm.

[@webyankee6558]

I believe companies rely on knowledge tests to much and miss out on the people who have natural talent to do or learn better than someone who has all the right answers. Thinking out of the box is a talent that you can't get out of a book.

[@keyofg2020]

@@webyankee6558 To add to this, I'm a scientist myself, but I don't memorize any of these kinds of formulas. If I use something frequently for a time I might, but that's it. Pretty much any kind of formula needed is readily available with a quick search on the internet, or in a book, etc. That's the benefit of technology. If I were the hiring manager, I would care more about one's ability to use the resources available to them to solve such a problem than the fact they memorized formulas to look smart.

[@insideoutsideupsidedown2218]

Amazons first question during the interview…. “Can you breathe on this mirror?” “Ah, ha.. i see you in the mirror and the moisture confirms you are alive.” “You are hired”

[@180fJC]

I worked for Amazon and was never interviewed, idk why. Maybe they just really needed people.

[@winstoncat6785]

@@webyankee6558 this problem relies on someone memorising a formula. There is a way to solve it using physics from first principles (force balance along cable) but without being given values for, presumably, a spring constant, you could only derive general solutions.

[@dontask8979]

It depends how many times I wrapped the cable around their neck

[@nsp932]

😂😂😂😂

[@markfryer9880]

Did you pull it up really tight till the light dimmed in their eyes?

[@jimgardner5129]

Hahahaha!!! Too funny. Well played.

[@oh-duh]

That's quite sadistic. Are you an accountant?

[@dustchip8060]

Lol

[@sinnistar99]

When drawing the diagram at 4:33 you can see that cable is 40m to the center and the pole is 40m above your x-axis, which intuitively doesn't work. Visually you can see that x would have to be 0. But who would stand 2 poles beside each other and hang a cable between.

[@xenomorph6961]

I found a slightly quicker method. I got a friend to help me with 2 50m long poles with an 80m long cable attached at the top of each pole. Then another friend measured the distance of the drop of cable in the centre between the 2 poles I and my friend were holding. Once it reached the required height from the ground we just measured the distance between the 2 poles! Easy and certainly quicker than doing the maths...

[@wdtony]

The answer for both is less than 80 feet.

[@amosdotl6892]

Are you superman or the flash?

[@xenomorph6961]

@@mraj9002 Bring my friends along obviously! I will get extra credit for thinking outside of the box...

[@booshallmighty]

@@xenomorph6961 You wouldn't get the job. They only want to pay people from the neck down. They don't want you thinking outside the box or anywhere else. They just want you to fill the box with product and send it to a van.

[@videyo098]

Ha but if you were asked the amazon question of 10m..you can solve it easily with zero maths in about 2 minutes. Meanwhile you'd still be playing with many friends, rented in construction equipment to erect two 50m poles! (Hint buy 60m poles so you can have at least 10m in the ground..and about 20 bags of postcrete mix!)..perhaps you could scale down and use 2*5cm drinking straws and an 8cm bit of string! But still..the answer is zero!

[@pharmesq]

You can estimate the 20m situation with Pythagoras. You end up with a right triangle of legs 30m (50-20 for the pole), x, and a quasi-hypotenuse of 40m. 40m is longer than the actual hypotenuse, because of the curvature of the cable - it does not follow the straight line distance between the top of the pole and the midpoint of the cable. But let's say we say "I don't know the caternary formula, by Pythagoras gives me a good first estimate." I think that's reasonable. 30^2 + x^2 = 40^2. 1600 - 900 = x^2. x = sqrt of 700, which is about 26.45m. The actual hypotenuse being shorter than 40m, you would say 26.45m (times two to get 52.9m) represents an effective upper bound on the answer. To get a lower bound, assume the cable has infinite mass and infinite tensile strength, such that it immediately droops to 20 meter off the ground, and then stretches parallel with the ground before reaching the other pole. Now you have a rectangle, with an x distance of 40 meters across (80 - 20x2 for each drop). So you can say for certainty that the distance must be between 40m and 52.915m. And the actual value of 45.4m ends up pretty well smack in the middle. Not exact, but quick, and not bad for basic math.

[@pholomotshidisi845]

Mike B 😂😂 that was my go to assumption. Too bad the margin was that huge for a single decimal answer.

[@Ethereal_rosegirl]

My answer was also similar

[@guillaumegaudin694]

Works like a charm for solution B though

[@zora_noamflannery2548]

- Glad I'm not the only one who over thought it.

[@jesselapides4390]

@@guillaumegaudin694 I mean yeah because you're just squaring and square rooting it

[@BluesInSeattle]

I've been a software engineer for almost 30 years. Anybody who asks me this kind of nonsense gets smacked with twisted tea.

[@coder0xff]

Agreed

[@laughingdog0]

Seriously!

[@holger_p]

Well, but if we ask you to draw this in an interactive chart, with one pole able to move sidewards, you are back to business ? The answer to the original question will only be a side-output then.

[@yashsvidixit7169]

How is this a non sense?? If you don't know or like Maths, does that make this useless? Humanity's tech keeps rolling only because these are people who know Maths very well.

[@holger_p]

@@yashsvidixit7169 No sorry, it's nonsense to memorize a formula you need once every 10 years. This ist old fashioned thinking to store everything in your head. It's allowed to use "external storage" like Wikipedia to look up, when needed. I mean, some exaggerate and need a calculator to compute 5*7. But computing 312*28 in your head, you can do for party entertainment to impress people, no job should depend on that ability.

[@tommunyon2874]

I know a catenary from a parabola, but is all I remember about math at this point in my life. Years ago I took the GRE and got tentatively accepted to a graduate math program, but if one doesn't use it, one loses it. These are great refreshers.

[@MickinMD]

As someone who taught geometry at one time and took refresher courses in multivariable calculus, I only watched the intro to the video, stopped it and calculated then watched video. The cable 20 m above the ground approximates two hypoteni (the plural of hypotenuse) of right triangles, which would make each hypotenuse 40, one side of the triangle is the pole from 50m to 20m which is 30 m and which would make the width of the middlle of the cable about 26.5 m from each pole by the Pythagorean Theorem x =sqrt(40^2 - 30^2) = 26.5 m. So it's about 53 m from pole to pole. That is in the ballpark of the calculation in the video, which is so complicated it requires trig functions and the quadratic equation, that I don't think there would be time enough to do in a job interview unless you were being interviewed for an engineering position and were given a test, not an interview. The 10 m is a trick question. In order for the cable to be 10m off the ground, there would be no distance between the poles because half the length, 40m would hang down from 50m height of each pole accounting for all 80 m of cable

[@dabest10]

Mickey Cashen just because u took time I’ll like ur comment

[@andyvan27]

That's what I came up with.

[@lobisw]

But the trick in the question for a) is precisely that you're asked for it to be correct to a decimal place, which means that linearising the curve would not work. You can see that because your answer is not even correct to the first significant figure. Even part b), because it's asking to a certain number of significant figures, makes you start trying to calculate. Which is obviously why it's a trick, and requires simple addition to solve if you think to picture it.

[@8304Hustla]

ive seen it on instagram, i think its exactly a question for hiring engineers. i dont wanna sound cocky but i had it in like 5 minutes. these kind of calculations is what you do on a daily basis in all kinds of engineering classes.

[@BipityBopity93]

Mickey Cashen That’s what I’m sayin...

[@WarpedYT]

I guess I wouldn't have gotten the job, no wonder why they don't have same day delivery anymore..lol.

[@jessstuart7495]

Here's the generic solution: Catenary equation: y=a*cosh(x/a)-a+h take the derivative and plug into the arclength integral... dy/dx = sinh(x/a) L = int(sqrt(1+sinh(t/a)^2),t,0,x) = int(cosh(t/a),t,0,x) = a*sinh(x/a) square this equation then use identity (cosh(x)^2 - sinh(x)^2 = 1) to rewrite. L^2 = a^2*sinh(x/a)^2 = a^2*(cosh(x)^2 -1) now manipulate and square the catenary equation... y-h=a(cosh(x/a)-1) (y-h)^2 = a^2*(cosh(x/a)-1)^2 Now divide the catenary equation by the squared arclength equation... (y-h)^2/L^2 = (cosh(x/a)-1)^2/(cosh(x/a)^2-1) using the exponential form (definition) of cosh(x) you can rewrite the right side... (y-h)^2/L^2 = (cosh(x/a) -1)/(cosh(x/a)+1) define b=(y-h)^2/L^2 and solve above equation for cosh(x/a) cosh(x/a) = (1+b)/(1-b) Plug this back into the original catenary equation... y = a*(1+b)/(1-b) -a +h and solve for a... a = (y-h)*(1-b)/(2*b) because we know cosh(x/a) = (1+b)/(1-b), and we know a and b, we can solve for x. x = a*acosh((1+b)/(1-b)).

[@Dollapfin]

Warped Perception of you knew 10,000 equations you’d be alright. Don’t worry dude I mean yeah you have to be a genius to do this but you don’t have to do this to be a genius.

[@macklemoore3153]

Jess Stuart yeah that’s why I changed majors

[@erichopper4979]

It took me about 45-60 seconds of thinking, but I'm nearly positive I know the answer, at least to problem b. But a would require more math than I'm willing to do right now. Though, if I'm not mistaken the shape the cable would make is a hyperbola. *Edit:* Almost right. :-) I was definitely right on b.

[@resourcetrafficking5819]

Eric Hopper So what's the answer

[@iyziejane]

Asking this question out of the blue is like testing whether someone loves mathematical history.

[@paulamsden8420]

If I were asked this question in an interview, I'd just linearize it and use Pythagoreans. ~53m.

[@holaholitadavid490]

Paul Amsden me too

[@shakingbabies5ever397]

JKay11235 yeah but Paul said linearize which means your answer is an approximation. I disagree with the answer because linearizing shows you that part b is just not possible because it's an impossible triangle, but it's still a fine start to a problem if you don't have random shitty formulas memorized

[@thegrabbler622]

JKay11235 that's why it would only be an estimation dumbass. Don't know why Amazon would expect people to be familiar with hyperbolic functions if they're just going to be moving boxes all day.

[@shraydn]

ShakingBabies5ever alternatively, look up the degenerate triangle.

[@shakingbabies5ever397]

Shraydn ok I have done so. To my understanding, it's just a specific triangle that serves the same purpose and yields the same result as thinking of it as a line in this case. The line is oriented directly downward if you want to be extremely specific

[@GaryIV]

Broke Mathematicians: hyperbolic cosine Woke Mathematicians: C O S H

[@Alche_mist]

As we here (Czech) call sine fully "sinus", I tend to call sinh "sinhnus". "Hnus" means disgust, as well as something disgusting. Such as sinh :-D

[@knight_23]

@@lautheimpaler4686 Nikal lawde, pehli fursat mai nikal

[@GeodesicBruh]

Illuminati 33 lmao Harry Potter spell

[@tantegreta]

Osh cosh b'gosh

[@chaos.corner]

Wealthy mathematicians: DOSH

[@philippeferreiradesousa8673]

Saying "kosh" and "cinch" can be classified as incitement to self-harm in my opinion

[@amazingpowers6056]

Really?

[@martinpattison8916]

Brings back bad memories of high school maths?

[@grahamjacob97]

I'm a naval architect so I've come across catenary problems many times with anchoring. I have written numerical methods that solve it (because in this day and age it's quicker. Then I saw the 1st problem at the end and instantly saw that they must be zero distance apart. If it wasn't after 10pm I would have done what you did and taken 10m from the bottom and come to the same conclusion

[@YonatanZunger]

... They're asking this as an interview question? For what? This is something I used to give as a homework problem for advanced freshman physics. I can't imagine what it would tell you in an interview setting.

[@3bydacreekside]

I can't imagine answering it

[@1anthonybrowning]

Yonatan Zunger it tells you the same thing it tells you about your freshman student. It tells you who can think, not just crunch numbers. BTW, I didn’t realize it either, so I guess I’m not as smart as I sometimes like to think I might be.

[@Tesskr95]

I suspect that (barring the fact that this was a trick question), the point of asking these questions isn't to see who gets it right, but the method people use to try to solve it. If someone just immediately throws the towel into the ring it tells you something useful (and you probably wouldn't hire them). If someone gets as far as splitting it at the centre and the coordinate system, but then doesn't know the right equation for the cable, of if they take some time to approach the problem in another organized way it tells you something about how they think. Someone actually immediately solving it would actually be a disappointing result, as all it tells you is that the person was familiar with the question.

[@ji23delgado]

Ummmm this is for the airplane engineering company called Amazon, not the online department store

[@arpitdas4263]

Don't give our bald master new ideas

[@yuppiehi]

Interesting. I took a totally different approach, by attempting to apply the pythagorean theorem, while chopping up the diagram into triangles, and I basically came to the same conclusion. The problem I ran into is that I thought I was doing something wrong, and never bothered to really look logically at the situation. For most of these kinds of problems, my number-one problem is confidence in my findings, and that's something I really need to work at.

[@AlgoTradingX]

I did not find the same answer using Pythagorean theorem. I got: 26.45751 times 2, which means 52 meters. I very doubtful about this video.

[@jakethompson4962]

Yes that's what I did as well.

[@richardmazkin9994]

@@AlgoTradingX that's because the Pythagorean Theorem doesn't account for the curve at the middle of the cable. I went the same route initially but had a feeling that it would have a measure of noise because that theorem assumes perfectly straight sides.

[@jonathanmunera2494]

Triangles don’t have curves…

[@michaelbrinks8089]

Cut a piece of string 8in (or 8cm) long then cut 2 pieces of string 5 in long to represent the poles. Place the 8in string between them and move them together until the 8in string center is 1in up from bottom of the two 5in poles.

[@steve_anderson]

When he got to the term "cosh" I bailed and went searching for funny cat videos. Don't laugh...I know my limitations.

[@kandaman304]

haha...lol. THAT was funny :-)

[@julianndavis9415]

I thought your ‘cosh’ was a typo. Til I got there in the video. I’ll be enjoying funny cat videos with you.

[@rohangeorge712]

@@julianndavis9415 i love this comment of urs, (wait for me).

[@ko-Daegu]

Hyperbolic cosine

[@Ccirgrg]

Is it supposed to be cos h? I'm confused Edit: nevermind. It's hyperbolic cosine

[@SarahPoulin]

Someone posted this on Facebook and after I figured it out to be 0 m, I found this video to see how other people processed the question. The way I processed it: Half the cable is 40 m, which is half the 80 m cable and also 50 m - 10 m = 40 m. So if I keep raising the bottom by 10 m until I get to the 50 m height of the poles, then eventually I get to 0 m for half of the cable. So the poles are 0 meters apart which is nonsense regarding the actual picture. lol

[@xIChaosReaperIx]

Everyone: *begins using trigonometry* Me, with a tape measure: "Where the poles at?"

[@stantonlee2266]

I’m never going to mess with an Amazon delivery driver again.

[@rsporsche]

again? do tell...

[@beau6113]

The people that answer this get a different job,

[@oh-duh]

@@beau6113 Exactly. Most likely, this isn't a required Q & A to be a delivery truck driver. Yet you should always be courteous to anyone who provides you a service you're too lazy [not in the case of disabilities or other hindrance] to go to the store & get yourself. Kind of like a sit-down diner, restaurant or bar. 😁

[@smartalek180]

Very wise of you. But it's not just the smarts. Like River Tam, they can kill you with their brains.

[@labadaba5088]

This question ain't for delivery drivers, this is for the software engineers, the brains of Amazons mighty machine!

[@Whitestorm2]

Amazon: "Entry level programming position" Also Amazon: "10 years of experience required"

[@SpideyNinety08]

As someone who interviewed with Amazon for an entry-level programming position, this is false.

[@Whitestorm2]

@@SpideyNinety08 Well you didn't say if you got the job or not so how could we believe you? 🤣

[@mahmudshamim1437]

This is a catenary problem and can be solved easily by using basic integration.

[@vedants.vispute77]

how?

[@michaeljarosz4062]

My high school math teacher warned that a catenary is not a parabola. The famous Gateway Arch in St Louis a catenary, not a parabola. People make this mistake because they have had elementary algebra but not hyperbolic functions, so they think it's x-squared.

[@mahmudshamim1437]

@@michaeljarosz4062 Every physics students learn the calculus of variation in their classical mechanics course. Where they solve this hanging chain problem by using Euler-Lagrange equation.

[@michaeljarosz4062]

Yes, but.....not everyone is a physics student!

[@mahmudshamim1437]

I agree

[@ThePortraitArt]

I kinda arrived at this conclusion due to first simplify the problem (ignoring any curvature and assume the cable is straight and bends once) effectively turning the problem into a triangle problem. Now I didn't think this would do anything but give me an approximation to work with, but an immediate problem based on this approach (involving the need to only look at half of the diagram) you have a right-angled triangle, where you know that the height is 40m, but the hypotenuse line (across from the 90 degree angle) also is 40m (the longest the cable can be, since it is under no curvature). That is of course impossible, unless they are the same line and it is not a triangle at all but a straight line. Which means the problem, only works if 2 poles is one pole and no distance and no area can be in between. Effectively arrive at the answer. Lucky maybe, but works.

[@cloud_strife8]

Actually, I did the same before watching the video. Then I tried doing it for case a) and got a different value, but it's comprehensible when you think about it: if you have actual distance between the two poles, there is a curvature in the center of the hanging cable, but if the two poles are together/only one, that curvature doesn't exist, thus making the two right-angled triangles approximation actually accurate.

[@williammeek4078]

@@cloud_strife8 If you solve case a assuming the cable is two straight lines, then use pathogens theorem, the answer you get is within 0.2 meters satisfying the requirement to be within one decimal place.

[@christophstegert8386]

I started typing this in, as I did the same, but then saw you got that, too. I wouldn't call that lucky but smart way to simplify a problem for approximation, which is very helpful in many cases. @william meek: It's not that accurate here: For the 20m case that gets to 40^2 - 30^2 = x2, i.e. about 26.5m, which is not very close but gives a first idea. Closer is assuming the cable as lower half of an ellipse. Circumference U is approx. pi * [ 3 (a+b)/2 - sqrt(ab) ] with a and b being the longest and shortest half diameters (admittedly had to look that up, too, but this equation is a bit simpler than the one from the video. If a = 50-20 = 30m, then, filled in, b = 20.4m, i.e. 40.8m distance between poles.

[@ThePortraitArt]

@@christophstegert8386 ya the whole "get within x percentage accuracy" kinda tricks people into thinking they have to use some method to approximate the curve and calculate a number. EVILLLLLLL hehe

[@mothercluckinbuttnuggets]

It works to a degree. The longer the distances the larger the error. For this problem simple Pythagoras gets you to the solution very quickly and easily.

[@238xblaze]

I’m a senior in mechanical engineering and have never used hyperbolic trig functions in my life. Seen them obviously, but no one uses them lmao

[@OrIoN1989]

Amen

[@mohamedquabbou5253]

lucky you, i used them a lot in quantum mechanics.

[@adolfodrago93]

God of Moisture J

[@NotYourAverageNothing]

God of Moisture Your name is hilarious.

[@osmanfb1]

cable problems, beams on elastic foundations are a few places in mech engr hyperbolic trigs are used.

[@subhampan4351]

Would like to see Bezos solve it first.

[@DrPepperJNL]

He pays someone for that.

[@defaultname01]

He can't solve a bung eye let alone math problems

[@ronlabe5487]

@@defaultname01 He employs a lot of people from Harvard.

[@oh-duh]

@@DrPepperJNL like an accountant 😂

[@DrLumpyDMus]

You don't get smarter watching other people getting smarter. Bezos learned that.

[@JohnDeaux]

Quick approximation would be Pythagoras. a²+c²=c². We know one side with the pole height(30 resp 40 meters) and the hypothenuse with cable length/2 as 40. That means for cable hanging in the middle at 20m we have 40²=30²+b² which can easily be solved

[@ainakwalajin1422]

Omg I did that too I thought I was wrong

[@falling_banana]

me too!

[@Ivorybilledwoodpecker1]

Me: Solves the problem Amazon: You're hired. Pay is 12 dollars an hour, mandatory unpaid overtime and no healthcare.

[@kjcorder]

Also. Here's your piss bucket and don't be late

[@subatomicparticle]

Amazon's minimum wage is $15/hour and its illegal to pay less than time and half for any hours worked over 40 in a week. Amazon is bad but not that bad

[@melancholyalexx7790]

@@subatomicparticle r/wooooooosh

[@ave3360]

Is 12 dollars or 15 an hour bad? Thats more than what I earn in my country lol and I have a "decent" position working as a financial analyst. And everyone makes similar to that..

[@kjcorder]

@@ave3360 in usa a financial analyst starts at $20/hr up to $50/hr or more

[@arashmoradian1988]

As a mechanical engineer, I would just use Pythagoras equation of a^2+b^2 = c^2 and call it a day, but good job factoring in the tangency!

[@d.bcooper2271]

But this is a serious underestimation.

[@pryo2460]

That's so wrong

[@jackalopewright5343]

@@d.bcooper2271 Exact answer = 45.2m. Pythagorean triangle = 52.9m, estimate down to 50m which is off the exact answer by only 10%. We can do the exact stuff later, but in a job interview or a team discussion no one has catenary equations near them and they don't have to. That is how a real engineer does it in preliminary design.

[@chillvibez7913]

It's a parabola U gotta study class 11 again

[@sergeyromanov2116]

Learn the meaning of "to one decimal place", "engineer".

[@CivilDefenseEngineer]

Amazon: "Please solve this problem." Interviewee: "This problem is a sinh." Amazon: "You're hired."

[@ovlv1518]

You need more likes cos you earned them :)

[@drcurv]

LOL, DTH. Back when I was at school, 'coshes' were OK, but sinh was pronounced 'shine'. How times have changed!

[@davidsirmons]

/me breaks out effing tape measure

[@divertechnology]

like i said after you.. that kind of math is very unusual these days

[@cindywu6645]

Funny cus the curve can be modelled by cosh

[@AskMarkieMark]

I had a similar interview question that wasn't quite as unpractical or unrealistic as this one. Mine was to determine how many laptops could be stored in the belly of an airplane for transit. Average plane, nothing military, commercial passenger aircraft. I needed to walk through my mental calculations out loud so the interviewer could hear my thought processes in arriving at an answer. By walking through what I'd experienced in the size of the laptop boxes, normal pallet size, and approximately how many pallets could fit underneath a plane, I got pretty damned close to the actual measured and calculated answer. In fact I was SO close to the actual answer, the interviewer was stunned. No one had ever been able to get that close just verbally walking through the variables. Still didn't get the job...

[@hamstring6792]

I have a 24" monitor, so the distance is 7.5" when in full screen mode.

[@nolinpanucci]

that's actually a very smart solution. You could have measured the paper in some way during the interview.

[@naderblack1114]

“a“ squared +”b” squared = “c” squared The square root of 40 minus the square root of 30, so 1600-900 = 700 The square root of 700 is equal to 26.4575’ that’s Half the distance of the seperation , multiply this number by two and you have appx. 52.9’ However this is NOT calculating for the radius of the fold in the cable where it reverses direction, which should increase the distance between the poles slightly.

[@HepCatJack]

You can get a little closer if you take a little off 40 say 38 if the cable was taut which would mean it would go lower than 20 meters let say by 5 cm. So you have 38^2 - (29.95)^2 = 546.995 take the square root: 23.39 times 2: 46.78

[@free99lolz]

Sorry guys I think they are doing actual math here. despite it being a trick question, you don't have to approximate. You randomly take 2 from 40 and then give the result in hundredths?

[@HepCatJack]

@@free99lolz not a random number. A random number could be 37 or 35 or 39 which wouldn't make sense. A plausible number is taken.

[@free99lolz]

@@HepCatJack Sure. This isn't a graduate math class it's KZbin, if you wanna use 38 u go for it. I was at work and maybe not in a good mood haha

[@gibbogle]

That is a very rough approximation.

[@TheMightyGiantDad]

So your answer is "look up the equation"? Pretty lame tbh. Loved part b though

[@zackariasdavis189]

Yeah i agree, "the solution of the problem is knowing the problem"?

[@Chilldude579]

Yeah I was thinking the same

[@petermuller7079]

@@zackariasdavis189 Better: 'the solution to the problem is knowing the solution' ;-)

[@user-tn2dk2pg2p]

@The Golden Legend The reason he didn't show it was because it requires physics to derive a differential equation for it and then differential calculus to solve it.

[@user-tn2dk2pg2p]

@The Golden Legend Btw math is for art that only few people can see - that art comparatively makes math more wasted for technology.

[@ayalatxaluma3789]

am glad i made it in 3-5 seconds using pythagoras square triangle formula. i knew it was an approximate but i soon noticed square of hypothenus was equal of square of the pole length, it is 40^2. then the other side should be 0 in length !! or pythagoras had been tricking me for my entire life ! lol ! thanks ! ayala & yami, shamanes associate

[@Striperbass2]

exactly....if both sides are the same length, they must be side by side.

[@Kommentiert_]

But the hypothenus isn´t equal to the square of the "pole length"? the pole length is still 50m. 😂

[@mehmoodulhassan4373]

But we can measure the length of base of the triangle...

[@BostonRoger]

The correct answer is... “Alexa, order a lazer distance meter” Wait for prime shipping and get an exact measurement. Done

[@dercooney]

correct answer is 80 meters or less, and at most, 50-10-80/2 it's a sneaky pete

[@muhammadnuralamsyah5601]

This is correct.

[@daapdary]

@@dercooney It doesn't work for part (a), where the cable is 20m above ground. In this case, the distance would be at most 50-20-80/2 = -10m, but the correct answer is certainly more than _negative_ 10 meters. :-) I estimated that the distance must be less than 2 * sqrt(700) = 52.9m.

[@user-ky6vw5up9m]

No - you are a mug because: You had to build the thing trial and error to measure it. You had to wait for delivery You spent money on getting the lazer distance meter. Your DONE takes too long.

[@factswithsatish]

Answer is 30

[@macgaming001]

Congratulations, you got the job! Now, to the warehouse with you!

[@thomask9673]

I'm an engineer and I don't even remember my hyperbolic equations. I look them up when I need them. If you get this in an interview, draw the same diagram, and then use pythagoras and tell them it's an approximation. If you work it out, you'll find the answers are close enough (like 5% error). Granted, the longer the cable, the more error you incur. That way you demonstrate you can use high school level math to approx solve an actual problem you might encounter if they asked you to hang a sign.

[@DanSlotea]

Good to know I'm not the only one that would have applied Pythagora's for a close approximate answer in thd first problem.

[@brendanoneil3489]

@@DanSlotea just what I did, in the real world a hanging weight would be pythagorean with the cable strectched tight surely? ...this 'cable' is more like a cantilever beam in it's bending ? not suprised their corporation tax is so low!

[@DanSlotea]

@@brendanoneil3489 funny how the same Pythagora's quickly triggers a red light in the second problem, where the visual representation is intentionally wrong to trick you. As soon as he put the numbers I was like what the hell?

[@brendanoneil3489]

@@DanSlotea typical amazon bs really..

[@kandaman304]

I know, right? I too am an engineer and this wasn't so easy to figure out right off the bat.

[@nicholasharvey1232]

Who else thought of using the Pythagorean Theorem here, treating the cable as the hypotenuses of two right triangles, with their bases being a horizontal line tangential to the lowest point of the cable. This may not be as accurate, since we're simplifying a curve into a straight line, but it should be a good approximation and Amazon would probably still appreciate our approach to the problem.

[@watermelonbanana1772]

Yes I tried this originally at first. Even though a simplification you can still find the trick that when you work out the numbers, the vertical and horizontal lengths of this triangle would both be 40, so we know something is up, and deduce the other length must be 0. I kind of got to here but didn’t think it was a trick question or say 0. Still glad I could actually think of that though lol.

[@TheDeathstar2000]

Before watching the video, I did exactly that and got 0 as a result. I thought I was wrong because of the thumbnail, only after I opened up the video and saw the image was made by the channel and that it was not provided with the question I understood what was going on

[@user-y2w3x]

I believe this is my first ever youtube comment in nearly 20 years... I'm so disappointed that a mathematician broke out an applied engineering formula without deriving it. I've watched many of your videos and can't remember another instance of no derivation/proof. What you did was closer to Googling the answer than solving the problem.

[@richardfeynman7491]

Exactly. Looking up formulas from someone elses solution is not a solution. This video should be retitled 'how to apply formulas'.

[@stickmenwithrayguns]

I'm with you on this. This should have started with a proof showing that the cable-mass doesn't affect the shape. Then derivation of the shape formula.

[@imienazwisko3630]

Congratulations on your first comment dude !

[@xxtwattwafflexx1]

KZbin is 15 years old if you start counting form the day the domain was registered.

[@DemolitionRepublic]

Who else decided to leave at the middle of the video but then decided to stay?

[@TheOzthewiz]

ME!

[@raymihulka8539]

Lol

[@Actionronnie]

I let the video play and read the comments,now I don't know the answer and really don't care.

[@Benedict00_ItchyManko]

I just sped up the video

[@JKFlaker]

I fell asleep 1 minute into it, once the math equations were started.

[@jallenpics]

No disrespect to my Amazon driver, but I'd be impressed if he solved this in an interview situation!

[@pedronorman5396]

Like many others have commented, I calculated the answer as two hypotenuses. Considering that this question was asked in an Amazon interview withouot concern for higher math, I must assume it was designed as a practical application of 8th grade geometry.

[@ExplosiveBrohoof]

Our boy Fresh Taulocker is descending into madness.

[@dmitryderbenev7759]

if you will draw a triangle instead of that weird figure you will get ~22,4m (in case of 20m distance) with a simple Pythagorean theorem, which is a quite precise result. And you will get 0 with 10m as well

[@tomfull6637]

Read my comments from 8 months back ;) ..the poles are 50 meters above the ground. Not 50 meters tall! 😂 The equation is a trick question

[@tomfull6637]

..or written by a person with poor knowledge of language

[@markzoned]

@@tomfull6637 It is a trick question with only one value for the distance the cable is above the ground 10m. Once you add another height for the cable but do not change any other values the poles can not be in the same spot. Which is what dmitry is trying to say. As far as the height of the pole, the way the question is worded the poles have to be 50m tall. The cable is hanging from the "top" of the pole which is 50m above ground.

[@jimspald]

OOps . 26.46 M with Pythagorean theorem. ..Not too precise.

[@Stew357]

I thought about doing the problem that way just for perspective; but you're right, it would have solved the problem. I solved for the angle between the adjacent side and hypotenuse with cos¯¹ and got 0°, the correct answer.

[@RayAdamsCanada]

oh darn, you mean; Amazon, the airplane engineering company, I thought you meant the online department store.

[@souloftheage]

Amazon soon will be all things to all humans.

[@FarFromZero]

6.3 million of the 6.4 million viewers had the same idea ;)

[@runawaypony429]

Hah, me too. I thought it was an interview for admins to see how they reacted under pressure. 😂

[@sanjeevyadav02]

I thought about Amazon forest🤣😂

[@KwizatsHaderach8]

As did I. Commented elsewhere, but it seems deliberately misleading. Principle of my argument stands.

[@abuzarov]

I guess the proper solution of 20m version should include deducing the exact function that describes the curve, based on forces of gravity and tension working on a unit of wire, and then taking an integral.

[@kindlin]

The curve is... a hyperbola. That's the common starting point here. As MYD points out, you just need to look up the equation for a hyperbola and solve it at the known [x,y] coordinate for the constant.

[@abuzarov]

@@kindlin how do you know it's a hyperbole? It's your assumption. You must deduce the formula itself, this is the essence of the problem. The rest is just calculation a monkey can do.

[@phobics9498]

@@kindlin Isnt that a parabola? Hyperbola would never touch the axis'

[@kindlin]

@@phobics9498 Unfortunately a cable does not hang in a parabola, that's more like projectile motion, as a classic example, a parabola is much easier to work with. No, a uniform, prismatic, tension-only cable takes the shape of a catenary, which is mathematically defined with the hyperbola. It does still have a closed-form expression, tho, so there is that. EDIT: A prismatic member has the same shape and material along its length; so, it's redundant with uniform in my list, as the the definition of prismatic means a _uniform shape_ and a _uniform material_ along its length. Anyways, I just had to clarify that.

[@matiasaraya5451]

Yeah i find that way more interesting. This can be "easily" solved by taking the langrangean (or hamiltonian) of the system and obtaining the stable points, wich would indeed be described by an hyperbolic function. Then, it's just a problem of describing the initial conditions of the system.

[@igfoobar]

If this problem appears on an interview for a job that does not involve cable management, then I don't want to work for them.

[@harshranjan8526]

Sir,they don't want to see your "Cable Management" ,they want to see how you observe the situations around you and how do you think about them.

[@ericdaniel323]

Did you watch the video? It's just a kid's brain teaser.

[@sinom]

If they ask question a I semi agree with question 2 they are just trying to weed out complete idiots.

[@Anichels]

This is 100% a logic problem. Perhaps you don't like to work for companies that value intelligence.

[@Rebius]

Nick Landry I like to work for companies that value intelligence, that doesn't mean I could solve the logic problem ;)

[@mjk8856]

“Sinch”, and “cosh”. I’m gone

[@c.o2307]

It’s actually pronounced “shine”

[@trusttheprocess4775]

Stfu it’s a sin hyperbolic function

[@RealCaptainAwesome]

That’s why I hate geometry

[@DogJones]

@@c.o2307 Sean Connery is that you?

[@bulgaria9003]

Sinh not sinch

[@XSebi0815]

if someone got the answer in the amazon interview, they didnt get the job bc they are overqualified and smart thinking people make it hard to exploid them with low wages.

[@Mellowyellow8888]

this is for corporate jobs.. or AWS portion..

[@AtlantaTerry]

"exploit"

[@TheBuddyLama]

No one is forced to work for Amazon, therefore Amazon cannot exploit (or exploid) anyone. Comrade.

[@pizzablender]

@@TheBuddyLama Except Amazon is pushing other businesses out. So ever fewere jobs there. And if they do that pushing by paying lower wages...

[@TheBuddyLama]

@@pizzablender My statement is still true. Amazon cannot force anyone to work for them or accept a wage they deem too low. I try to buy locally from local businesses, but they rarely cater to me, which is fine, they must focus their resources where they deem appropriate, just don't blame me for not buying goods I don't want.

[@nautaki]

Most companies hiring for a semi-numerical role (i.e. pretty much every role in a technical firm) tend to ask questions like this one from my experience. This includes 99% of the financial services firms plus their competition in the hiring market (i.e. the tech firms like Amazon, FB, Google etc). The outcome of the interview is a function of the number of candidates versus how quickly they want to hire versus how long the hiring manager wants to stay with the firm. If there is only a few candidates, they are desperately looking and the manager is on his notice period expect a quick hire even if you don't know what a meter is. On the opposite end of the spectrum, expect not to be hired even if you are Einstein himself if they are not too serious about hiring (whether they know it or not). So how can they not be serious about hiring yet be conducting interviews? a) they are gathering street intelligence (they want to see what the competition is up to and what kind of people are they losing and why) b) they have the budget to hire and the HR has asked them to do so but the hiring manager can't be bothered - yet he likes being pampered by the recruitment agencies c) rejecting a candidate with a PhD that can pluck unicorns out of thin air and he is cool and experienced boosts the superiority complex of the hiring manager how might be a school drop out who just happened to be stuck with the firm because he has nowhere else to go. Despite what they want you to believe, most firms, and that includes big investment banks, have zero guidelines around the exact questions that can be asked other than things that can land them in a lawsuit (e.g. are you pregnant?). Therefore, the hiring manager most of the time asks what their ego dictates including questions like this one. When all is done and you are hired after 10 rounds, expect to be spending 99% of your time raising JIRA tickets and writing 0 interesting code with any sort of direct impact to the firm.

[@hotkayz]

And what would happen under typical conditions (moderate supply and demand, hiring manager is not on notice)?

[@bigchrisXl]

My answer would have been "I am a very reliable worker. I show up on time and I make sure to get the job done."

[@y2ksw1]

It's a good choice. If I was checking in new employees, you would get the job.

[@irokeeee]

At least, this would give you a more simple job. But if you are supposed to develop algorithms or optimize business processes......

[@trains4george]

Always on the lookout for 'trick' interview questions. I answered this in less than a minute. However, turning the tables when asked if I had any questions, I asked "How do Amazon pay less tax than me?" Needless to say, I didn't get the job.

[@boyuan3904]

nowadays, many interviews become a show of the interviewers.

[@erickfrago7224]

I was actually wondering why such question is included on the interview, whereas this may be more appropriate for a test. Interview should focus more on the behavior quewtions and analyzing a candidate's employment history

[@prasadbmvs]

Its a show off

[@brinckau]

But still, this question can help you find those who can think, instead of just crunching numbers. Moreover, being interviewed is also a show. So it's fair if the interviewer is playing the game too.

[@edwardmonsariste4050]

Pamm. No? Pamned... No? Pam mnd.... hello lady.... You shut up!!

[@codecampbase1525]

It’s what happening when you give one side full power without regulations. Add your average student to a position like this and you have your circus show. Laws must always protect the people first, then the interest of companies.

[@JLujan4492]

This is great. I teach physics and from part a, without really doing any math, I guessed it would be around 50 using a flawed thought process of using the pythagorean theorm, which 45.4 rounds up to. But with part b, before I thought about how to work out the problem, I thought to myself, "why is the cable so far down? That makes no sense," and I didn't have a mathematial guess for myself. So seeing you explain it all is pretty funny.

[@nickn7939]

Good point, I'm not a math expert at all, but also the fact it droops down over half the radius. It is an elliptical, half would be 25m, so it droops with 20m left. So the shorter diameter part of the elliptical (idk the correct term for this) connects the two poles. If it drooped 25m, it would be 50m apart, but it falls a little longer at 30m, so the poles are less than 50m apart, and probably not too much more. From that alone one could guess btwn 40-48m or so.

[@yousefbaytam6213]

"Fool us once, shame on you. Fool us twice, shame on us. Fool us 3 times we take you to the parking lot and kick your ass" (Penn Jillette, 2018)

[@serajalhorani838]

😂

[@nitrofish1974]

Are you sure this is required two box packages and put tape on them.

[@diaryofaplantkiller]

Only if the tape your using is 40m long and has minimum stick while the box in question needs 80m tape to close. Now if it is throw back Thursday you may be able to get more tape if you posted about your MCM.

[@SuperThest]

Amazon also hires engineers and programmers

[@rowlffffff]

And they are generally not well packed or taped.

[@mariav.3227]

😂

[@bumfist88]

My thoughts exactly xD When I think amazon i only thing about slave warehouse workers being exploited by this corporation.

[@hopelovebreathe]

Does knowing the answer to this question help you to stand on your feet for 10 hours with no bathroom break better.

[@Conan_the_Based]

And do you have to answer it again after your 9-month contract expires and they make you wait awhile before rehiring you, just so they don't have to permanent position you and pay benefits?

[@19speed57]

depends how low your pecker hangs nnd what your inseam is plus the height of your shoe heels.

[@mannyechaluce3814]

It helps just in case you need to pee where you are and hit the target bathroom 10 feet away :D

[@yogeshsolanki6661]

Here is a short trick.... only if you don't remember this method 1. look at the chart at 2:30 2. we can see a right angle triangle.... 3. use Pythagorean theory... (AC)² = (AB)² + (BC)² here, AB= 30m AC≈ 38m (it's 40m but it it loose wire so assuming -2m loose) Now… (AC)² = (AB)² + (BC)² (38)² = (30)² + (BC)² 1444 = 900 + (BC)² (BC)² = 1444 - 900 (BC)² = 544 BC = √544 BC ≈ 23.32 Now Double it to get distance.... ≈46.65

[@carultch]

That's not a triangle. Cables don't hang in straight lines, so the apparent hypotenuse of that apparent triangle, is not a line at all.

[@YoursTrulyGajodhar]

how did I get here, I was listening to pirates of the Caribbean theme song I don't feel epic anymore

[@tr1ckster726]

Anany Shrestth omg I died when I just read this hahahahh

[@christiantebbe6284]

Same. I literally just watched a vocal coach react to a song, and now im onto this

[@mayankpatel1053]

And i was watching the youtube rewind.

[@mindslayer6810]

Anany Shrestth dre

[@highestraad3241]

Anany Shrestth lol😂😂😂😂😂👍

[@chinareds54]

If we assume the cable was measured to 80m while lying flat on the ground (ie with 0 tension), then it is possible for the poles to be some distance apart due to the stretching of the cable under its own weight. The distance will depend on the stretchiness of the material making up the cable...

[@tychowozniaki9269]

Aaron Driscoll It's not an assumption. It's a statement

[@djbmw1]

Aaron Driscoll i fully agree! I hate that many educators are taking math equations and adding real-world elements and stories, looking for a single answer.. all while they've opened it up to interpretation and exploration. Silly silly people thinking that they've got a clever way to trick people when all they've done is created a question where more questions are need to be asked in order to approach an answer

[@darrelllogan1274]

djbmw1 I don't think he's wise to your cleverness. But, I appreciated it. Made me chuckle a bit. Haha.

[@djbmw1]

Aaron Driscoll very true. Funny enough, if anyone looks at my channel they'll be able to see my 350 foot zipline where cable sag and stretch is a VERY real thing. Let's not even get into the forces applied to the two anchor posts and the deflection that they will experience simply from the weight of the cable (without applying any additional tension on it) ;-)

[@macmcleod1188]

Fester Blats only if you assume spherical cows.

[@letsplaysmr8621]

If two poles, each standing fifty feet tall, are strung from top to top by a freely hanging cable of zero mass, why don't you want your workforce to organize.

[@Audio_Simon]

As an engineer I think people should draw it accurately!! After looking at the thumbnail for 2 mins I thought something is misleading because even Pythagoras tells me it's not right.

[@princedesperado7787]

You could actually transform the cable into a straight line and make a triangle using one pole , half of the cable and the distance between the pole and halfe of the cable. And get an answer as well. But it is not going to be exact of course.

[@xavdel0]

I think drawing it accurately is false because all is a representing something, the note should be the only accurate data

[@princedesperado7787]

Yeah I know. It is just one possibility. The right solution is using a coordinate system. Like he presented. That is what I did as well. But my problem was getting to the equation.

[@Alexc99xd]

I remember on NPR car talk, they had this same question with 75m poles and a 150m long cable and said how far apart does the poles need to be for the cable to just hit the ground. Needless to say my friends looked up some formulas for catenary and was dumbfounded when they got the answer

[@Alexc99xd]

Alright, I misremembered the problem but here it is www.cartalk.com/node/44836 Still, same trick as the video

[@TheSnakeIsSolid1]

They need to be teaching them how to deliver a package unopened.

[@TheOzthewiz]

Or, learning how to figure the exact trajectory so the package lands IN the bushes!

[@ocalavictory3728]

Lol

[@RKBock]

sooo... your answer to "how to solve the question" is: look up the formula online. great job! I learned a lot in this video.

[@darnellyiadom3596]

Based on that intro, I guess a lot of people have been saying your name wrong

[@celsorosajunior]

Darnell Yiadom isn't it Presh Talker?

[@trasicworld2545]

Celso Rosa no it isn't 😂

[@tomtrask_YT]

I never dared try - fortunately the name of the channel, MindYourDecisions is a lot easier to tell my math loving friends about.

[@kinfongyeung5400]

isn't it Fresh Tallwalker?

[@rifqi-realexperience5179]

I though it was press talwalker xd

[@davidb5205]

In the 10m case (in the thumbnail), wouldn't the distance be 0? The cable isn't long enough since half of it is 40m which is _just_ enough to hang 10m above the ground when hanging from a 50m pole.

[@Noreceipts400]

I guess you were one of the only ones to get it

[@davidb5205]

Noreceipts400 - Well I only got the problem in the thumbnail. I wasn't even close to getting Problem A. I didn't know the catenary formula and I haven't used "sinh", "cosh" in forever.

[@jaideepsingh4660]

Noreceipts400 😝😝😝😝😝

[@alexismandelias]

David Boucard that's precisely what I was thinking

[@Hephaestus_God]

I have no idea if you posted this after watching the video or before and I can never trust anyone anymore after this

[@kineahora8736]

This is one of those things where if it comes up in a trivia quiz or a quick interview, it has to be 80 or 0 just because those are simple cases that can be reasonably asked...

[@justinwhite2725]

No. If it were 80 the line would be taught (50 m above the ground). Although yes now that you mention it it has to be 0 for 10 meters because half of 80 is 40 which leaves only 10 m left.

[@desolatedreams21]

@@justinwhite2725 but what would 20 be?

[@justinwhite2725]

@@desolatedreams21 watch the video. It's actually interestong that those that know the math get 10 wrong, it those that don't know the math can deduce 10 intuitively.

[@desolatedreams21]

@@justinwhite2725 10 is more of an IQ/problem solving question than a math question. It’s meant to make you think logically 20 is the polar opposite

[@keplar-bnewgen2564]

@@desolatedreams21 if 10m is 0 m apart and 50m is 80 m apart. Then 20m will be 20m apart as the cable will lift 5 m for every 10 m distance between the 2 poles.

[@doncnyman3683]

I believe the accurate answer to the 10m question is ""The cable would not be only 10m above the ground". The 20m question assumes a parabolic curve, which recognizes the physical characteristics of a cable, whereas the 10m question ignores the fact that any cable, no matter what diameter, must bend into a curve when turned back upon itself, reducing the effective length. Therefore the 80m will always be more than 10m above the ground. Of course, one can assume the ability to pinch the bend, but one could just as well assume a heavy enough weight to make two straight sections in the 20m problems, and therefore a simple trig solution.

[@Ew72Qa]

My exact thoughts.

[@vijayviharbandari6624]

This problem is actually also studied by Electrical Engineers to measure sag in power transmission lines( transmission lines get expanded due to temp and other factors ) . The catenary equations are also studied as a part of it. Having said that, rarely we do use those or solve these types of questions as these are deemed very practical and only done when required and not for general exam or interview purpose.

[@christopherwalsh7700]

Did this for days as part of my bare handing training.

[@artvandelay0073]

Here's a sample question from a job interview I once had: "Why is a man-hole cover round?" I answered "To cover a round hole," and walked out, never looking back...

[@davew4998]

The answer is so that the cover can't fall through the hole. In case you ever want to look back.

[@javierdager]

I would say round is the most efficient and stronger construction That’s why is round.

[@artvandelay0073]

@@davew4998 // LOL...I knew your answer was most likely the correct answer at the time, but I just couldn't resist being a wise-ass with the answer I gave. That "interview" was actually a 10-question test/quiz. Nine of the ten questions were math-related, and the tenth and final question was about the man-hole cover. The only person that I actually spoke to that day was the secretary/receptionist who handed me the test and to whom I gave it back when finished. The job was for a manufacturing engineer position with CAD design experience.

[@davew4998]

@ashutosh Mishra Hi. No, if it were rectangular it could fall through the hole, as the short side is shorter than the long side, and definitely shorter than the diagonal . Even if it were square you could be unlucky enough for it to fall down through the diagonal. A round one can't fall through whatever angle you try. If you have a rectangular tea tray you could draw around it and then see how you could pass it through the drawn shap if it were a hole. (Yes I know, some manhole covers are indeed recdangular. Guess the makers aren't concerned about safety so much. Ps. Remember that yhis is a 3d problem, not a 2d one. The man hole cover can be rotated upright through 90 degrees and then dropped.

[@davew4998]

@ashutosh Mishra My pleasure.

[@GammaFZ]

4:58 they’re a complex distance apart, then. You just proved it

[@annoholics]

Thanks for solving the puzzle. Now you can start filling boxes in an Amazon warehouse near you. 👍

[@ckm-mkc]

My answer to this question is to ask if my job will involve hanging cables... Because if it doesn't, then this question is irrelevant.

[@sjonnieplayfull5859]

The problem has a simple answer that does not need complex calculations. They want to know if you can see a simple sollution, or get stuck in rules and regulations.

[@TheOzthewiz]

Actually, if you were the "cable guy" letting that cable hang THAT low and NOT moving the poles farther apart, you would be fired for not following code! Electricity is dangerous!

[@RochesterOliveira]

I kinda knew this was a trick when I noticed that if we assume the cable is straight (forming a triangle) the hypotenuse is as big as one of the sides. So the other side has to be zero (a^2 + b^2 = c^2, if a=c then b=0)

[@thelimbo3829]

5:04 No! You do not have to think "logically". The parameter "a" in this case is simply infinity! This corresponds to x=0 !

[@2ezay681]

Its a hidden coordinate system and you point the lowest point on 0. So yeah: x=0

[@mmwapec]

In a interview you better think logically first, you can't go through the calculation. He was just explaining.

[@nguyenbanghia8970]

I was worried about replacing my high-end older oasis with this one kzbin.infoUgkxCgPI5O2AtmcHq9SJhgsCGbpAzJAJfrJp but it is surprisingly light and the screen resolution is just as good. I never had the warm light on my old kindle, but i do not use it on the ipad so I will probably not need it. I think the only thing I'll miss is the self-adjusting light, but this is so worth it!

[@sparkeyjames]

Answer is a question: What real world problem would this solve for a guy driving a small van delivering packages?

[@Mystikan]

Figuring out whether or not it was safer to drive over a suspension bridge or take a ten mile detour and drive over the arch bridge instead? ;)

[@carlfrye1566]

@@Mystikan Only the bridge engineer/builder would know that answer.

[@dezznutz3743]

@@Mystikan Wouldnt it be best to know the height of your vehicle and the bridge clearance? It doesnt take a Quadratic equation to figure that out.

[@TheOzthewiz]

@@dezznutz3743 Considering the number of semi to overpass crashes, not too many drivers. On the other hand, maybe they are doing these calculations while driving!

[@IJChan223]

I missed it on my physics 101 exam ~4 years ago. So it is a fairly standard physics/math question a software engineer candidate would possibly get.

[@deusdark1]

For length problems, I first asked myself what are the boundaries of possible answers. First thought, 80m line... 80m apart. Then I asked, if I put the poles together, what is the amount of slack i'd get (would it hit the floor, would it have a lot) Then I realized that if X is zero, then we'd be at 10m... poof. Done. I guess it was a lucky approach?

[@sofabuddha]

@@CalebBerman Grow up. Get this god of yours to make an appearance.

[@HarleyKimber]

@@CalebBerman didn't close your speech marks... God awful grammar 😉

[@oweifhtuvj975]

@@CalebBerman Time to put down childish things and pick up interesting things like brain teasers and math problems.

[@sofabuddha]

@@CalebBerman Your god does not exist. And thank god for that be ause Yaweh was a monster. Look at the way you accept blood magic rituals and human sacrifice. You've lost your humanity on a lie.

[@Quimerateck]

I'm probably too lazy to make the math, so i would've endup doing a scale version irl of the poles

[@liselieder562]

I got similar results from considering the sagged cable to be in perfectly still environment as a semi circle (180 degrees of a circle with 160 M circumference) with the bisected midpoint 20 m off the ground for my mental image. Then I overlaid the Pythagorean Triangles to orient the poles & radius of the Semicircle. I calculated by hand solving for B or Radius & confirming by plugging the values for either the B side from Pythagoras Method into the Circumference Formula (C = 2πR) where 160 m as C is known & 3.14 for pi. The second problem was a problem from the mental image because even changing the curve to a parabola opening UP, the gross measurements of the beginning diagram were not possible to have both the length of the cable stay at 80 m & the poles 50 plus the limiting factor of a 10 m gap from the ground. Before getting into harder math it was clear the original diagram had to be altered. I am certain this was more of a "how do you handle a stressful situation" exercise, problem -solving skills & communication exercise plus perseverance & the measure of out-of-the-box thinking. I think it's important (at least for me) to understand the "how" & "why "of answers of one cannot recognize an figure that may be orders of magnitude wrong. I don't ever want to have to calculate Sine & Cosine even with a slide rule & found the simpler methods enough.

[@InjuryAndDestroying28]

Finally, a normal guy

[@guilloguzmanl]

nice!

[@superdudewizard750]

This is silly. You just pulled a formula from the source without understanding or being able to convey the physics behind the formula’s derivation. A bit more effort and thought would have led to a much better video.

[@robertjohnson4401]

AdeptLink I agree. If the problem cannot be solved by basic math with common sense, it should not be presented. Looking up a specific formula is the same as just looking up the answer to the problem. I simply approximated the hanging string as straight lines forming a vee shape. Then you have a right triangle that can be solved.

[@craigolson1822]

Not accurate, Robert. Use RMS sinusoidal formulas.

[@regards7229]

Totally agree

[@Jim-ei2iv]

The problem can be solved with commonsense without the use of much math at all. Generally, an interview question like this is designed to find the kind of person the author of the video is - someone who dives into a complex procedure without first thinking about the basics of what we need to solve. Generally, if you see a question that seems complex, first look to see if it is some kind of trick or if there is a simple solution. Thats usually the case. A lot of time can be wasted on stuff like this.

[@grasspunk]

The problem a) that needed the equation was _not_ presented in an interview. The video guy added it in for fun. I doubt many CS candidates will have memorized catenary formulas and as you say it would not be a good interview question. The real interview question was part b) that did not need a formula just a bit of common sense.

[@zuzusangry7129]

One way to first approach a problem like this is by considering extremes in order to gain intuition on how the described system works: Consider how to maximize their distance apart: that would mean stretching the cable with maximum tension such that it is still 50m above the ground in the middle, resulting in the poles being 80 meters apart. Now, what of the other extreme? What happens when we put the poles in the exact same spot, or coincident, such that the distance between them is 0? Well, the cable would simply drop down half it's length, or 40m, then go up to the other pole for the other half for 40 more meters. Since it drops 40m, that would make it rest only 10m above the ground -- which happens to be what this question is asking and we have already solved the problem without trying to remember some strange kosher formula. :)

[@Jim-ei2iv]

This is exactly right. No complex memorization of formulas is needed or expected.

[@benevolenthighwayman882]

Except for two problems. The first example assumes that there is either no gravity or that the cable and poles are infinitely strong. The second example ignores the fact that a cable suspended from both ends will form a loop, rather than fold perfectly in half. This means that the cable will never reach down to 10m.

[@hectorgreenville5201]

I agree with you. My suspicion is that the solution requires deduction or logic rather than math. That "to one decimal" is also probably just a mechanism to throw you off course. I would even go so far as to say that it is impossible to solve with math because it is a cable. How heavy is the cable? How thick? How stiff? Changing any of these changes the solution. As you have already mentioned the answer for 10m is 0m apart, but we still need to solve the one for 20m. Let's say we stretch the cable out, the cable would be 50m off the ground and the poles 80m apart. Now let's say we need to get the rope to 30m off the ground, which is halfway between the 10m off the ground and the very top at 50m (10m to 50m is the possible range). Logic would suggest that in order to achieve that you have to move the poles 40m apart, which is half of the 80m maximum. You now have a similar situation. 20m sits halfway between 30m and 10m. Half the 40m once again and you have a final answer of 20m apart to get the rope 20m off the ground.

[@mrWhiskerssss]

Yeah I think the guy in the video missed the point of the employer asking this question... it’s meant to assess on the fly reasoning and problem solving, not to assess wether or not the applicant comes with a calculator and an oddly specific memorization of one single cable formula. Lmao

[@untyrhallsprung569]

Hector Greenville I like to think of it like this: You have 80m rope length to distribute along x and y (think of it as spending, like a currency). If you distribute along x that costs you single rope length. Along y costs double rope length. This can simple be deduced by the extremes (0 distance means 0 distribution along x, 40 distribution along y, because what goes down needs to come up again), for 80 distance (x) there is no slack to its 0 distribution along y. Now if the distance to ground is 20 that means the rope-distribution in y is 30 (50 -20) which is basically the slack for one half of the rope, so double that as slack for the entire rope. That leaves 20 meters to distribute along x (80-30*2) and distribution along x is just another way of saying distance between poles.

[@bsm6776]

All that math to put stuff in boxes

[@intexclouds9607]

brutal.

[@JM-yx1lm]

JKay11235 they must not be too smart if they are working just like slaves.

[@biuku]

Ya, that’s all that Amazon did.

[@TiMoN0908]

They didnt ask these qustion a normal delivery guy. Amazon has a lot of IT employees working in the Silicon Valley and earning huge money.

[@monroefive-o40]

My wife works at Amazon in Ga. They didn't have a written test interview. She had a verbal interview and was hired on the spot two years ago!

[@giannispetalotis7298]

b) I would start from b. And as you correctly mentioned the distance is 0m. a) *When the distance is 0m the rope is hanging 10m above the ground. *When the distance is 80m the rope is hanging 50m above the ground. *The rope will be hanging anywhere between 10-50m above the ground. *Given the above, when the distance is 40m the rope is hanging 10+(40/2)=30m above the ground. *And when the distance is 20m the rope is hanging 10+((40/2)/2)=20m above the ground.

[@steventortora4487]

I did not know i was applying for a civil engineering position lol

[@HattoriHanzo031]

Did you watch until the end of video?

[@steventortora4487]

@White Wolf true,but if im applying for a box handling postion this question serves zero purpose.

[@gigaferz]

I figured it would be a question for high end positions, But if that question is for any and every applicant, that means If you Answer It Correctly, It will definitely will ring a bell , There's a purpose for it.

[@19Koty96]

@@steventortora4487 The question serves to weed out people with freezing-point IQ.

[@ChadCarney-hu3du]

@@steventortora4487 when box handlers put 40 pound kettlebells onto the wrong belts to where they fall off and kill a man(yes this happened) you start to consider the thinking ability of your employees