Viral logic test from China

[@electrocubic5116]

What a coincidence! This same question was asked to me in a university entrance exam I gave today (they just changed up the names and heights of the objects) and I had watched this video like 3 yrs ago, so I didn't exactly remember the method, but after reading the question, the solution just popped into my mind and I solved it in a minute! Now I can know for sure that I did the right thing! :)

[@Horse_In_A_Suit]

i..... isnt this supposed to be elementary school math?

[@danquaylesitsspeltpotatoe8307]

The answer in China is the same for both one of your meals has escaped!

[@thebirdfromtwitter1249]

University entrance exam? Isn't this just a basic simultaneous equation

[@CarsFer]

I felt too proud of my self solving elementary school math questions

[@rcb3921]

If there were a candy reward and I'd solved this faster than the kid... I definitely would have considered keeping it for myself.

[@gabigolpc5626]

Me too

[@Anywaytimetorecord0.]

@@rcb3921 imagine Every 10 questions=1 girlfriend 🗿

[@aaaaaattttttt5596]

@@Anywaytimetorecord0. imaginary or real?

[@Anywaytimetorecord0.]

@@aaaaaattttttt5596 for motivational purpose take it seriously 🗿🗿🗿. maybe you will not get a gf but you will able to become Einstein.

[@portalsrule1239]

Solved using algebra. Going in I thought it was going to be impossible because of the three variables but was quickly surprised with how well it worked out.

[@bettyswunghole3310]

As soon as you spot the trick that the combined height of the cat and the turtle is in fact one variable, it becomes quite easy.

[@ilovecats3807]

But its for elementary school 😭

[@szczur03]

It's just 1 variable, but with extra steps

[@khairinazrin]

The moment I saw 2 variables cancel each other, I can't help but "Bruh".

[@RangerCaptain11A]

there is no variable in the problem. each item is a fixed measurement. you used elimination and substitution to reduce the three measurements down to one.

[@ElNerdoLoco]

As a construction electrician, I have a lot of measurement shorthands I know work but have forgotten the principles behind. I knew averaging the heights would remove the cat and turtle as variables, but didn't immediately know why until I saw your visualization.

[@christophsiebert1213]

That's what I did. I averaged them out, and then proof'ed my answer with the visual approach. Idk, why I didn't immediately think about making it an equation.

[@ElNerdoLoco]

@@christophsiebert1213 I've run into lots of people who like to turn everything into equations lately. Especially younger people. I'm curious if that's how they teach now. I went up to calc 2, but my first approach is to still just recognize ratios or other relationships between numbers and plug the numbers in that way. I save equations for when things get more complex.

[@christophsiebert1213]

@@ElNerdoLoco I mean, equations ARE the language to calculate in. If we just go by eye and ratio, we can make errors. Even if slightly, those errors get propagated through the system and get bigger. So, working with equations from the outset, that you know how to use, should be the way to go, imo. But of course, this is for the real serious stuff out there. For something silly and fun like this here, you can go whichever way works, as long as you can proof the result with a separate method, best case an equation. I got teached calculus by learning ratios visually and later on got more and more equations. And I think that's right. We should just not forget that one can start off solving problems more simple and comfortable.

[@averagegatsby]

Yeah, as a mechanical engineer I looked at it, and did the same thing. But I didn't have a lot of confidence in my answer at first.

[@AxillaryPower2]

I went about this the other way: I formed the equation, noticed that the solution was the average of the two, and tested with other heights to make sure it wasn't a fluke.

[@tabletoparcade4203]

I love that some of your videos are simple while others counterintuitive. It forces me to remain critical even when I the answer appears simple.

[@SpaceyFCB]

Never going to China, I'm too short to sit at a table of 150cm.

[@商昱鹏]

A 150cm table has nothing to do with China

[@aravindvissamsetty]

@@商昱鹏 I'm not taking any chances.

[@BakaBaka8146]

What if its not table but cat's tree?

[@DivyaAtul]

Yes mee too

[@jeroenaarts85]

LOL, I recognized your name. Funny you follow this channel too :D

[@mansellindustries273]

Presh, I’m just a Dad of two Primary School boys. Twice a week I take you problems to the school and we solve them with the kids who love maths. So in regional Australia you are inspiring kids to love maths more!

[@paulkennedy8701]

Good for you. (I mean that genuinely.)

[@Felixkeeg]

^Pin this Presh

[@111076tom]

great!

[@souradeepdey1338]

I love maths too

[@BeddableLibra]

Paul Kennedy have you ever been used Brilliant?

[@MindYourDecisions]

Whoa, this video really took off! I'm also seeing my problem shared on Twitter and other places, but sadly they cropped out by logo! If you see something like that, please let everyone know of this video. They will surely love my other videos and will help more people discover this channel. Thanks! You can say something like, "See the original problem and more great videos on MindYourDecisions at kzbin.info/www/bejne/eIG1pph5qpiZjrc"

[@roscoepatternworks3471]

Another way to solve. The difference between 170 and 130 is 40. Divide 40 by 2 = 20. Add 20 to 130 or subtract 20 from 170, and you get the answer. 150cm

[@frankteng]

I solved it after I saw the notification picture, couldn’t help myself damn Chinese genes.

[@athletico3548]

I found the same result this way: y=height of the cat x=height of the turtle M=height of the table M=170-y+x (1) M=130-x+y (2) M (1) =M (2) 170-y+x=130-x+y 40=-2x+2y 20=-x+y y=20+x (3) M=170-y+x (1) M=170-(20+x)+x M=150cm

[@akramhussein5006]

How u can find the cat and turtle tall? from the same picture

[@alexandre9673]

Could you explain why are you adding 20 to 130 ? What is your argument in relation with the height of the table ? Thanks. Some people answer that the cat must be 40 cm...which is correct... but they can explain why !

[@crowbar_the_rogue]

The most difficult part about this puzzle is figuring out what such a high table could be useful for. Edit: They make standing desks that big, I looked it up.

[@thassalantekreskel5742]

Must b e a standing desk.

[@crowbar_the_rogue]

@@thassalantekreskel5742 150 cm is a lot even for a standing desk. Many people are shorter than that and wouldn't even see what's on it.

[@Roonasaur]

I'm American, so I am just blissfully unaware :)

[@crowbar_the_rogue]

@@Roonasaur 150 cm is about 5 feet.

[@Roonasaur]

@@crowbar_the_rogue TY. :) (I could've googled it if I really cared, lol, but thank you)

[@royschering1140]

With T = height of table, C = height of cat, and S = height of snapping turtle: 1) T + C - S = 170 2) T - C + S = 130 Subtract 2) from 1) 3) 2C - 2S = 40 or C - S = 20 Substituting 3) in 1) T + 20 = 170 so T = 150 C can be any height as long as it is 20 cm taller than S. The key is that you are solving for T and (C-S). Two equations and two unknowns. Of course, rewriting 2) as T - (C - S) = 130 and substituting will give same result.

[@jakemccoy]

Just add your first two equations at the top and you get 2T = 300.

[@royschering1140]

@@jakemccoy Solving for C - S or T is equivalent. Either way works.

[@MindYourDecisions]

1 million views! Whoa, this video really took off! I'm also seeing my problem shared on Twitter and other places, but sadly they cropped out by logo! If you see something like that, please let everyone know of this video. They will surely love my other videos and will help more people discover this channel. Thanks! You can say something like, "See the original problem and more great videos on MindYourDecisions at kzbin.info/www/bejne/eIG1pph5qpiZjrc"

[@The_Viral_Hug]

MindYourDecisions verify the results plzz

[@balubalu7718]

well its great u found out the height of the table......... but can u figure the height of the cat........ and also the height of the turtle ?

[@Sadoc_M]

Wait! Okay, I got the same answer, but when I check it, I kept getting the turtle to being 0cm long... how does a turtle get to be ZERO cm long? What am I missing here??

[@burritogunwhale]

⁠​⁠@@balubalu7718cat=30cm turtle =10cm Height diff between 130 and 170=40 Turtle is a bit smaller than half the cat Turtle = 1/3 of cat 10=1/3 of 30 170-30+10=150 130-10+30=150

[@akaRicoSanchez]

I figured it out and even found both methods! The problem is that I am no longer an elementary school student...

[@justarandomcatwithmoustache]

Rico Sanchez same here😅😅

[@harshitkumar4760]

Me too

[@saecsee]

Now. Let's calculate the volume of air(20%O2) necessary for burning 200g C2H6O (70% pure) under the conditions of 2 atmospheres and 30°C.

[@jeetshannigrahi5315]

@@saecsee on it. Class 10 reporting here.

[@ishaanbhoj]

same and irony is i teach in one...

[@MindYourDecisions]

Thank you for 1.1 million views! Happy 1 year anniversary!

[@foxyeipiccolicolpidigenio9099]

I love when you say "Did you figure it out?"😂 Anyway, I solved it! Thank you!

[@unalcetiner8783]

can u figure out what ln (-1):i is?

[@roberthakurralte2638]

Could you please tell me, how tall is the cat and tortoise

[@UJJWALKUMAR-ud3lu]

I didi that.. The second way is 😎cool

[@NAGENDRAKUMAR-pt7zi]

What is the height of cat and Turtle

[@bbelilovsky]

As an engineer, I'm glad to know that my manual algebra skills are still intact.

[@madcowusa4277]

Q: How do you know somebody is an engineer? A: Wait 5 minutes and they'll tell you.

[@bbelilovsky]

@@madcowusa4277 That’s a fair observation, not gonna lie

[@sth6027]

same lol

[@philipmcniel4908]

I initially solved it by using algebra (too quick!), but then I came up with a different visual solution, this one based on subtraction: You can see that when you go from the first drawing to the second, the bottom of the bracket gets higher by the difference between the turtle and the cat. The top of the bracket also gets lower by the difference between the cat and the turtle.. Because of this, the difference between the two brackets is two times the difference between the turtle and the cat. Since the difference is 40 (170-130=40), the difference between the heights of the turtle and the cat must be 20. That means if we replaced the cat with another turtle in the first drawing (so that there were two turtles instead of a turtle and a cat), the measured height would be 150 instead of 170. Of course, the difference in height between the turtle on the table and the turtle on the floor is just the height of the table, since those turtles are both the same height if not for the table!

[@snailedEJ1]

I am glad to see that I was not the only one that utilized this same visual solution using subtraction!

[@Cowtymsmiesznego]

I mean, this is literally algebra too xd It's just a different solution to the same system of equations.

[@jeffn9952]

Good logic

[@gaelrocha1613]

I solved using logic but, accidentally, used algebra. I thought that the difference was 40cm, so the cat must be 20cm taller than the turtle(because the 130cm on the second picture it is due to a 20cm taller from the bottom and ends 20cm higher too, 40cm in total). Then I figured, if we put a cat at the bottom and a cat on top, the difference between their heads will be the tables height. Resulting in 150cm(170cm-20cm when replacing the turtle's height and likewise in the second picture). I dont know if I explained myself, but I'm happy I figured it out.

[@mingofishygaming8684]

Oh I solved using systems of equations: (t = table c = cat r = turtle (r is for reptile but I already used t)) r + t - c = 130 c + t - r = 170 Using algebra, we can see that the difference in height caused by switching the turtle and cat is 40 cm, and half that height will come from the added height of the cat, the other half from the subtracted height of the turtle, so the difference in height from the turtle to the cat is 20 cm. Therefore c - r = 20. This can be rearranged to c = r + 20 Substitute: (r + 20) + t - r = 170 r's cancel, 20 + t = 170 --> t = 150 The table is 150 cm tall.

[@wizinjsh]

I did this one two also. But my other method was made without any calculations in my head. Just put both pictures on top of each other (x2). You get 2x table - cat + cat - turtle + turtle=300. So 2x table = 300. 1x table = 150. Edit: hahahhaha... and its the first solution in video.

[@Khantia]

I (almost) accidentally found the answer xD Wrote the problem down, and tried to add (x + c - t = 170) to (x - c + t = 130) which got me a 2x = 300 => x = 150. But doing that wasn't my original plan... just something I decided to do after writing it down.

[@DeFaulty101]

I did it differently. The difference between both heights was 40cm, which told me the cat must have been 20cm taller than the turtle, thereby resulting in an addition or subtraction of 20cm from the height of the table, which told me the table was 150cm. I take tremendous pride in the fact that the answer came to me in what felt like 10 seconds, maybe 15, but certainly under 30.

[@kirakira9906]

Well it's not really an answer but an arbitrary decision. The cat could be even 22.5cm taller, who says it's 20 besides you?

[@freddybobtheknight]

That's how I did it too.

[@skilz8098]

@@kirakira9906 I used the same method he did. The total height with the cat on top is 170, the total height with the turtle on top is 130. This is a difference of 40. The Average Difference in Distance is 20. (A+B)/2 = C is an average distance and it is relative. Here we have 20 as the relative average difference in distance. Then we can use that average distance in height to determine the height of the table by either combined heights simply by subtracting from the taller height or adding to the shorter height seen by these to equations: 170 - 20 = 150 or 130 + 20 = 150. This is equivalent to the algebra method by taking a + b - c = 170 and adding that to c + b - a = 130. Adding the two equations cancels out both a and c leaving 2*b = 300 resulting in b = 150. It's the same deduction just a different processing of achieving it. In many cases there are multiple algorithms to solve each problem.

[@MrOarson]

@@kirakira9906 No, it must be 20cm. 150 + cat - turtle = 170. Therefore, subtracting 150 from both sides yields the equation cat - turtle = 20cm.

[@dnuma5852]

@@kirakira9906 If you subtract the equations you get Table-Table-Turtle-Turtle+Cat+Cat=2*Cat-2*Turtle=40 cm Then you divide by 2 on both sides 1/2(2*Cat-2*Turtle)=40/2=Cat-Turtle=20 cm Therefore Table+Turtle-Turtle-Cat+Cat=Table=170-20=150 cm

[@maraudershields283]

Given the swapping of variables for each example, I knew the answer would be in the middle of 130 and 170, so 150. The hard part was figuring out how to prove that it was.

[@JamesTDG]

Exactly my situation, I can find the solution easily in my head, proving it for me is like trying to calculate a new digit for pi

[@darowizna_od_tatusia6585]

You could have just add 130+170 and devide it by 2. Your result is an average height which is also a correct answer.

[@TheMisterGuy]

That's what happened to me too. The correct answer jumped out as the average between the two, but I felt the urge to prove it algebraically and get Cat Height in the form Turtle Height + Height Difference so I could do the problem after having proven it.

[@parththakkar4719]

x+y-z is 170 x-y+z is 130 Therefore, 2x is 300 and x is 150 Algebra rocks 😅

[@anandelight]

Same here

[@Carl-LaFong1618]

I knew that.... I just didn't want to say anything.

[@flatmajor6802]

*Then says it anyway I wonder why? HMMMMMMMM

[@samuelasamoahboateng4306]

How did you combine the two equations

[@snadarsh33]

@@samuelasamoahboateng4306 since there are 3 variables and 2 equations you can take one of the value as 0. Eg take z as 0 then 2x=300 , hence x=150

[@philipcollier4883]

I really like this one. I used a visual method as well but just treated the turtle height as "0". Then the 2 equations are table + cat = 170, table - cat = 130. Got the same answer that way

[@dielaughing73]

That's a really clever trick. 'Let [variable] = 0' is a typical mathematical technique, but it's not necessarily intuitive to imagine a turtle of zero height

[@txcpnae]

Why does the hamburger have legs?

[@jameswong3318]

r/cursedcomments

[@anamuslimah-7658]

I'm laughing

[@57thorns]

To be able to jump off the table to switch places with the cat.

[@Iuru4B]

Because it is a Cheespider

[@Frisbieinstein]

To keep his pants up.

[@FloorTileMan]

I did it a different visual way and got a different answer. In the first picture it shows 170cm being from the top of the turtle to the top of the cat. That means that the 170cm doesn’t include the turtle’s height and includes the cat’s full height. Then in the second picture it shows the cat on the bottom and the turtle on top with the 130cm not including the cat’s height and fully including the turtle’s height. If you then make the second picture fully include the cat’s height and not include the turtle’s height like is shown in the first picture the 170cm would then go from the bottom of the cat to the bottom of the turtle which is just from the bottom of the table to the top of the table. Therefore the table is 170cm.

[@nathancorso4067]

I started solving with algebra, then i figured out a simplier and quicker solution with logic: Top turtle to top cat = 170 Top cat to top turtle = 130 The difference is based on the height of the cat: it's taller than the turtle by 40/2 (caused 1x its tallness is subtracted when switching cat with turtle on top of the table; another 1x is subtracted when switching the turtle with the cat on the bottom of the table), so the height from turtle to turtle should be 170-20=150, but it's the same as floor to top table height

[@TheAskingCow]

i dont know what i did but I believe this comment sums up how I got there haha

[@robertzappe9747]

It is not 150cm. It is 170cm. The cat has 70cm and the turtle 30cm.170cm - 100cm = 70cm. 130cm - 100cm = 30cm. 200cm - 30cm =170cm. The table is 170cm high.

[@nathancorso4067]

@@robertzappe9747 that's impossible, 'cause top turtle to top cat is 170 cm and the turtle and the cat are not of the sane height (otherwise top cato to top turtle should be 170 cm too, but instead it is 130 cm).

[@Prvosienko]

What I did was that when going from 170 to 130, you shorten this distance by (cat-turtle) on both sides. Therefore 2*(cat-turtle) = 40, therefore difference between height of cat and turtle is 20. From the second picture, if we now put a cat on a table instead of turtle, we know it will be 20cm higher = 150 cm. Then we can move it all down one cat, and see that it's the height of the table.

[@jfezz1726]

Did the same thing almost. I used algebra to solve for the height of cat/Turtle

[@mko6965]

Yep this is pretty much what I did.

[@Nuoska]

Here's another solution. Let x be the difference between the height of the cat and the height of the turtle. In the first picture if you replace the cat with a turtle or the turtle with a cat, the distance will be reduced by x. Replacing both animals will reduce the distance by 2x. Therefore 2x = 170-130 x = 20 Now you can either add x to the second picture or subtract x from the first one to get the height of the table.

[@rifqi-realexperience5179]

Im also using that method, but in algebra A(table)+C(at)-T(urtle) =170 A(table)+T(urtle)-C(at) =130 ___________________________ - C-T-T+C =40 2C-2T = 40 2(C-T) = 40 C-T = 20 ________ A+C-T=170 A+20=170 A=170-20 A=150

[@aifesolenopsisgomez605]

I assume you have to use elementary level math, or else is kinda cheating...

[@Esablaka]

@@aifesolenopsisgomez605 that is elementary level math. if a child got a good understanding for math these basic algebraic equations shouldnt be a problem for it.

[@ck3908]

too convoluted answer, way more simple than this.

[@aquamarine245]

Great explanation. Simple and concise

[@JoshuaSheik]

It’s interesting because the visual one at the end was actually the same as the algebraic equation method

[@JamesDKyrts]

The fact that the same subjects appear in both situations, and in each case they swapped places in a 1 for 1 matter, means that you can use the mean equation to figure it out. Which might be closer to the second method. But it takes less time to calculate, than the time given by the "pause the video" phrase...

[@johnsmith-dn8zm]

y know when I looked at this problem I immediately thought this was gonna be easy but and it was, however after realizing that the stuff that I learned in high school is being taught to elementary school students in china, it expanded my views on the world. this was very enlightening

[@ysf-d9i]

I got perfect scores in Canada-wide math contests back in high school and consistently scored top 50 in the country for my grade. If I went back to China, I'd be a below-average math student. And not just slightly below average, I'd be one of the worst in the class.

[@dielaughing73]

India too. They do advanced maths years before we do in Australia

[@orcheastra22]

I learned how to tie my shoes in elementary

[@suryanshsingh4533]

I don't know how to tie shoes in high school

[@HackedPC]

@@suryanshsingh4533 true . Me too.

[@skbrianff6733]

Same😂😂

[@gabereese8645]

The way I solved it was a little different. I noticed that when the turtle and the cat are switched, the height between them changes. Using the first image as a reference, the height between the cat and the turtle in the second image decreases on the top and bottom by the difference of the heights of the cat and the turtle. Using this, we can deduce that 130cm plus two times the difference of the cat (which I'll call "c") and the turtle (which I'll call "t") equals 170cm. Written better like this: 130+2(c-t)=170. Simplifying, we get c-t=20. The difference of the heights of the cat and the turtle is 20cm. After this, I took the second image and wrote it for the height of the table (which I'll call "T"), which turned out like this: T=130+c-t. We've already established that c-t=20, so substituting it in gets T=130+20, which is 150. The height of the table is 150cm. Christ that took way too long to write 😑

[@dielaughing73]

Yes it's interesting that you can find the difference between the cat's height and the turtle's is 20cm, but you can't solve for their heights beyond that. The turtle could be literally any height, one centimetre, a mile, and the result for the table would still be the same. It frustrates mathematical thinkers because they immediately see it's impossible to solve for the whole system as you usually would, but there's still an answer for the quantity requested

[@Yotanido]

I rearranged the second equation so it gives the height of the turtle and substituted it in the first. That worked, too, but adding them is probably a lot easier :D

[@kirakira9906]

How did you do that?

[@bitcoinweasel9274]

I did the same.

[@shiah]

@@kirakira9906 probably something like {cat + table - turtle = 170; table + turtle - cat = 130} | 2 > turtle = 130 + cat - table -> 1 > cat + table - (130 + cat - table) = 170 -> cat + table - 130 - cat + table = 170 -> table + table = 170 + 130, so table is 150

[@potatogaming7044]

For the first one I did, T=turtle and c=cat T+ 170 -c, And C+ 130-t Change to 2t+40= 2c Divide on both side T+ 20= c Change all the cats in the original equation to t+20 And simplify

[@tomassousa3104]

I didn’t use any of those methods and still got it. Here’s my thought process: the turtle and the cat simply switched places, so half of the difference between 170 and 130 would be the difference between the two, which is 20 cm, then we take the top turtle (130-20=110) and add two turtles to substitute the cat (110+2x20=150) and that would be the height of the table

[@prologikus]

Sameee

[@aliquida7132]

Same - the cat is 20 cm taller than the turtle, so the height of the table is either 20 cm shorter than 170, or 20 cm taller than 130, both of which adds to 150

[@skilz8098]

@@aliquida7132 Not necessarily. The cat could be 30 cm tall and the turtle could be 10 centimeters tall and this would still give 150 for the table. The cat could 32 cm tall and the turtle could be 8 cm tall Why do both cases work? The height of the cat and turtles are unknown and they are relative. What is known is that the difference between the two stacked heights including the unknown height of the table is 40 cm and since there are two variants, the Average Difference In Distance between the two is 20. You can either subtract the this average difference in distance from the taller height or add it to the shorter height and both will give a result of 150 cm which is the height of the table.

[@evelynivy6124]

@@skilz8098 You're right about the general logic here! You've got one trivial error that threw me off in trying to understand what you were saying, though-if the cat is 32 cm tall, the turtle is 12 cm tall, not 8 cm. The numbers you used are ones that sum to 40, not ones with a difference of 20. But yeah, for all we know the cat is 350 cm and the turtle is 330 cm. Or maybe the cat is 6 cm and the turtle warps reality to be -14 cm. All we can figure out from the given information is that the values differ by 20, so we can't rule out even extremes like these. And if you plug these values into the equations, the solution still works :D

[@ethanmiller5105]

Great video! The second visual explanation help me finally understand the logic of adding two equations to find the value of a variable.

[@ethannguyen2754]

I think I found my doppelgänger

[@Fidooop]

So I concluded it was 150 but my method was realizing the 40 unit difference between the two values meant the cat was 20 units taller than the turtle (at least that was my hope, thankfully that's a really big turtle) Then I looked at the picture with the turtle on top and added 20 units to imagine it was 2 cats and no turtle existed. From here I had the measurement of the table, 150, it was just offset by one whole cat hahah

[@Packerfan130]

Let X = table, C = cat, and T = turtle. We have X + C = 170 + T and X + T = 130 + C. Add these two equations. Then 2X + C + T = 170 + T + 130 + C. Then 2X = 300. Then X = 150.

[@rodigoduterte9192]

I think this is a correkt answer

[@RobertShield62]

I did the same

[@ketalciencia3163]

That's what he did..?

[@Below10IQ]

I had the same exact variables and same exact set up lol.

[@Below10IQ]

@@T3tr4gr4mm4t0n Because of the equivalence relations. If a=b, adding a to bothe sides is the same as adding a on one side and b on the other.

[@pNsB]

I got it pretty quickly by arranging method 1 in a certain way. Two equations in the form x+y=a, x-y=b. In this case: Table + (Cat - Turtle) = 170 Table - (Cat - Turtle) = 130 Which shows that Table is directly between 130 and 170, so it's 150.

[@TheAndreyCraft]

I've seen only preview, but the answer is 150cm a - table, b-cat, c-turtle a+b-c=170 a-b+c=130 If we will sum the parts we will get 2a=300 a=150

[@David_Hardy]

I dont know why i found it so funny when he said "now we can erase the animals from the picture".

[@aeromodeller1]

You must be very careful how you do that. If you erase the cat, the turtle will have a height of -20.

[@louf7178]

David Hardy Yes, because he removes himself from normal imagination into rigid, mathematical operations mode.

[@imhulki463]

LMAO

[@billy.7113]

In Singapore schools, pupils use *bar drawing* method. This is a simple one, even for kids.

[@clovisyio6573]

Yay models yay

[@timsecond]

How this method works? Measure using a scale bar?

[@hxcq5883]

Nobody said it was hard. And education in singapore is very stress

[@likerandom8030]

I feel like im Einstein when my answers was right :D

[@anshumanagrawal346]

Ikr

[@critisizerr245]

@@anshumanagrawal346 ikr mtlb

[@anshumanagrawal346]

@@critisizerr245 I Know Right

[@belfiore1495]

Yes

[@jenybhatt3415]

🐈= cat 🍽️= table 🐢= turtle 🐈+ 🍽️- 🐢= 170cm 🐢+🍽️- 🐈= 130cm (Adding both we get) 2🍽️= 300cm Thus 🍽️= 150cm (Elementary student's guide😁) I solved this when I was 13. At that time it was famous on Facebook...

[@MasterController123]

What is CAT, TORTOISE HEIGHT..?

[@dosu5064]

It's looks like you wanna a cat and a turtle for dinner

[@RT-yz9fp]

I didn’t even think of trying to solve it with an equation even though it makes perfect sense to do so. I just tried to solve it the visual way and eventually realised I might have to stack the tables. When I did the solution suddenly became clear.

[@prashp143]

Made a lot of algebraic mess and still couldn’t come up with a proper answer. I started with Cat + Table - Turtle = 170 - (Cat - Table + Turtle = 130). It ended up giving me cat’s height as 150😂. But after reading comments, I went back, and solved that the cat is 30, turtle is 10, and the table obviously is 150.

[@daerdevvyl4314]

Actually there isn’t enough information to calculate the cat’s or turtle’s heights. We know that the cat is 20 cm taller than the turtle, but that could mean that the turtle is 10 cm tall and the cat is 30 cm tall, as you stated, or the turtle could be 15 cm tall and the cat 35 cm tall. And although it’s far fetched, it works out mathematically for the turtle to be 500 cm tall if the cat is 520 cm tall.

[@dickottel]

the turtle is 5 cm and the kitty is 25 cm, 1 year old and he's so cute and fluffy, it's obviously a chihuahua. trust me, I'm mathing in my sleep bro.

[@ib9rt]

A simpler visual method. Imagine both cat and turtle are the same height. Then both measurements will be the same, and will each be the height of the table. Now imagine the cat grows a bit taller. One measurement will increase by some amount, but the other will decrease by exactly the same amount. So the average of the two measurements will not change and will remain equal to the height of the table. Therefore the height of the table is the average of the two measurements.

[@abdallaahmed780]

This comment is underrated

[@tibfulv]

Indeed, this is illustrated by the addition of the two equations.

[@z01t4n]

@@tibfulv Yes, but it's a bit more intuitive = more suitable for youngsters. If I had been forced to solve this problem with a pen and paper, I would have used the set of equations method, but since I wanted to solve it in my head, taking the average seemed to be the obvious way.

[@parshwanathmirji8703]

Can u show it through equations

[@abhilast6629]

Wow !!! Same thinking bro !👌👌

[@Renteks-]

First one of these I've properly figured out! All it took was a VCE Maths Methods level of learning for an elementary problem lol

[@knotwilg3596]

Put these two structures on top of each other. On its left side, that whole structure is: table, cat, table, turtle On its right side: turtle, 170, cat, 130 So 2 tables equal 300 and the table is 150.

[@gartackpsdav4984]

My method was simultaneous equations. T(able)+C(at)-U(turtle)=170 T-C+U=130 Add the equations to get 2T=300, T=150

[@aeromodeller1]

This is interesting because we appear to have two equations in three unknowns, which usually we would consider not solvable. When I first glanced at the thumbnail, my mind said, both at the same time, "That's unsolvable. That's easy." ;-) The diagram method is exactly the same as the algebra method. It is like using rulers to add numbers. The animals should not be taken away before moving the bracket, though. It is clearer if the upper leg and the lower leg of the bracket are both moved down by one cat height. It can also be done the other way, with the turtle on the top of the upper diagram and the bottom of the lower diagram, and move the bracket down by one turtle height. This corresponds to summing the equations in the reverse order. It also gives a hint into why this is not two equations in three variables. The height of the cat and turtle do not matter, as long as they differ by 20, they can be anything. We are not trying to solve for three unknowns. Two of them are still variables. If we had additional information about the height of the cat and the height of the turtle, like their sum or product, we could solve for those heights as well.

[@RandomPerson-yq1qk]

Let me show one way to visualize why we can know the third variable that you may not have thought about yet. We have 3 equations so lets think of a 3 dimensional room. We have a x,y and z axis. Each of those represents one of our 3 variables. Each solution is a ordered number triple (x,y,z) which means that each point in our room is a possible solution. Now we introduce our first equation. We can think of this equation as a plain. Only points on this plain satisfy the equation. Our second equation is another plain. As long as our two plains are not parallel they will cut each other in a line. Only points on this line satisfy both equations. This line can have the property that it is in a 90 degree angle to one axis. In that case the value of the variable associated with this axis is the same for all points. This means that there is only one solution to this variable. This is exactly the case in our problem.

[@aeromodeller1]

Visualization is a good idea. We already know what the graphical solution looks like; it is a line perpendicular with the table axis at a value of 150 and which projects into the cat, turtle plane as a line which intercepts the cat axis at 20 and the turtle axis at -20. We can see this as the intersection of two planes; first the plane perpendicular to the table axis at 150 and second, the plane perpendicular to the cat, turtle plane through the projected line in the cat, turtle plane just described. The described solution line has one value for the table height and an infinite number of values for each of the cat and turtle heights. This isn't exactly what you described, you described it with two different planes. Following your original thought, the two intersecting planes may be described more particularly as follows. Both planes contain the solution line described above. The plane corresponding to the first equation passes through the cat, turtle plane, where the height of the table is zero, on the line which has cat intercept 170 and turtle intercept -170. The second plane passes through a line in the cat, turtle plane on the line which has cat intercept -130 and turtle intercept 130. These two lines are on opposite sides of the origin, they are parallel and the corresponding planes lean toward each other to intersect on the solution line described above. Either of these pairs of intersecting planes is a strong visualization of how there is one solution for the height of the table, but an infinite number of solutions for the cat and turtle heights.

[@EnsignJC]

@aeromodeller 1 I am also fascinated that "There exist some 3 variable problems with 2 equations, whose exact answer/value can be found for 1 variable." That's something NEW to me! Like you, I previously believed that you can either solve for all 3 variables IF AND ONLY IF you have 3 linearly independent equations, or none at all if you have less than 3 equations. This problem proves it wrong. I can see now after having thought about it why this problem is solvable for Table. Because by chance it is a 2 variable - 2 equations for Table, if you make the equations like this: Table + (Cat - Turtle) = 170 Table - (Cat - Turtle) = 130 If we rename (Cat - Turtle) as DIFF ... the difference in height btw Cat and Turtle Table + DIFF = 170 Table - DIFF = 130 This is a 2 eq - 2 var problem. Both Table and DIFF are solvable to be Table = 150 DIFF = 20 = Cat-Turtle

[@EnsignJC]

@Random Person Your explanation is quite useful. I've never thought of it as "the answer line is in 90 degree angle to one axis.", though. I would just describe the answer line as a line in 3 dimensional (x,y,z) space, whose coordinates satisfy the following line equation: y - x = 20, z = 150 Essentially and visually, it is a line y = x + 20 in 2 dimensions, flat x-y plane, floating at the z - height held constant at 150.

[@aeromodeller1]

Table = 150 DIFF = 20 = Cat-Turtle and y - x = 20, z = 150 are different forms of the two equations that correspond to one of the pairs of intersecting planes that determine the solution line; first the plane perpendicular to the table axis at 150 and second, the plane perpendicular to the cat, turtle plane through the projected line in the cat, turtle plane. Both of these equations in this problem contain all three variables, sometimes hidden. Cat - Turtle + 0 x Table = 20 contains Table multiplied by zero, so all values of Table satisfy this equation. When Table = 0, this plots in the Cat, Turtle plane as the line with Cat intercept 20 and Turtle intercept -20. This same line is valid at every value of Table, so this equation represents the plane which is perpendicular to the Cat, Turtle plane through the projected line in the Cat, Turtle plane. Similarly, Table + 0 x Cat + 0 x Turtle = 150 is satisfied by all values of Cat, Turtle, but only one value of Table. This is the plane that is perpendicular to the Table axis at 150. The intersection of these two planes is our solution line, in which Table = 150 and Cat - Turtle = 20. It is interesting that we have two sets of equations and two corresponding sets of intersecting planes producing the same solution line.

[@paulkennedy8701]

I wrote out both equations, but I ddin't add them. I disregarded the table as the common element in each equation. That showed me that the difference between cat-minus-tortoise and tortoise-minus-cat was 40. Given that the differences had to be symmetrical they had to be 20 and -20. So the height of the table was 170 minus 20 and also 130 plus 20. (Cleverer or more practised people than me would have been able to think through this almost instantly of course.)

[@peterhimin8051]

that exactly what I did

[@ArcheREE]

Saw the thumbnail, challenge accepted. As is custom, I tried it myself first. I wasn't sure how it would go since I never learned logic formally, but I also know sometimes math'll getcha by. Made two equations from a visual interpretation of the two sides of each of the two equations presented. I'll use A for table, U for turtle, and C for cat. On the left, we can plainly see that A + C = 170 + U, and on the right A + U = 130 + C. A starting point! Solve for A, so in the first we subtract C from both sides and get A = 170 + U - C, and on the second we subtract U from both sides and get A = 130 + C - U. So we have two equations, both of which equal A, so we can substitute for A and determine the two equations equal each other. So 170 + U - C = 130 + C - U. Subtract 130 from both sides and we have 40 + U - C = C - U. Add U and C to both sides and we have 40 + 2U = 2C. Divide both sides by 2 and we have 20 + U = C. Our first milestone! We have new knowledge we can start over with, so we'll go back to our original formulae and replace each C with U + 20 So going back to our original equations and replacing variables with our new knowledge, we get A = 170 + U - U - 20 or A = 150. If we're right, the other equation should work. Checking, A = 130 + C - U or 150 = 130 + C - U or 20 = C - U which is the same as our earlier 20 + U = C, so it checks out. The interesting part is the cat and turtle height aren't static. As long as the cat is 20cm taller than the turtle, no matter the arbitrary height assigned to either, the equations both work with a 150cm table. Came to check the comments once I was convinced I had it. Now I'll watch the video where they probably talk about all this, rendering this comment completely moot, but it's KZbin comments so we'll post this before watching a single second. Did NOT get the math right on my first pass, for the nonexistent record, but felt the mistake happen, and found it while checking my work. Left the erroneous math out of the post for clarity.

[@jackofalldrones9653]

My brain must function weirdly. I solved this by first finding the height difference between the cat and the turtle, which is half the overall height difference. I got a 20 cm height difference. I used that to calculate the distance between head tops if it were two turtles by adding 20 cm to the distance if the turtle is on the table and the cat is on the floor. I got the correct answer of 150 cm.

[@NotKnafo]

d = table c = cat t = turtle two equations: d+c-t=170 d+t-c=130 add both you get: d+d+c+(-c)+t+(-t)=170+130 calculation result: 2d=300 divide by 2: d=150 table is 150

[@beatrizquental5971]

I did it visually but thinking like: 170cm had the same size of the 130 + cat, so the cat is 40. Then I made this equation: 170 - cat + turtle = 130 - turtle + cat, and so figure out that turtle = 20. Finally, I just did the equation’s sides and both were 150

[@nanangmuhammad2067]

Nice... It is Same with this.. You can eliminate, where h= table... h= 170-cat+turtle h= 130-turtle+cat ------------------------------+ 2h=300 h=300/2 h=150

[@dannypipewrench533]

I used the algebra method, but decided to add 40 to the table with the turtle on top, to equate the two figures. I then defined cats in terms of turtles, and decided that the cat was 20 taller than the turtle. Using this knowledge, I replaced all cats with turtles, and then all turtles cancelled out. This is why math is fun. Many ways to get an answer.

[@ameensh2439]

As soon as I looked at the problem, my intuition told me the answer is 150. But then I solved it slightly different.. 170-130=40. 40/2=20 you can add 20 to 130 or minus 20 from 170 and you'll get 150. Also, the reason why I came up with this method is because mathematically the cat is taller than the turtle by 20cm so if the turtle is 10 the car is 30cm.. the difference in height is 20cm and when you flip their position the twenty doubles and thats why we have a difference of 40cm between the first and the second height.

[@wallace3199]

I used algebra but somehow took atleast 15 minutes doing the complex way Here's how I did it: Distance from top of Tortoise and top of Cat in the first picture is 130cm and in 2nd picture it is 170cm then height of cat is 40cm. Then from first picture height of table is 130cm + tortoise height. You can confirm this by compering the same with second picture. In the second picture height of table is also 130cm + tortoise height as the cat's height is excluded. But height of cat is 40cm, then in the 2nd pic distance from tabletop to cat top is 130cm - 40cm + tortoise height = 90cm + tortoise height. Also in the 2ne pic, given distance is 130cm. Therefore, (90cm + tortoise height) + tortoise height = 130cm which means height of tortoise is 20 cm. Now from either pictures, adding the remaining height of the tortoise height of table is (170-40+20=)150cm in the 1st picture, and (130-20+40=)150cm..... THANK YOU

[@LoscoX]

As linear algebra student I had some difficult to understand how could solution be possible even if the linear equation were just 2 instead 3, having 3 variables, but then I've realized that this problem has infinite solution because, even if the high of the table is a constant value of 150 cm, the high of the turtle depends by the high of cat or vice versa, according to the rouche capelli theorem. And that explain why some people have found the right solution even choosing an arbitrary high for the cat or for the turtle.

[@Fullmetalminos]

Is it bad that I figured out the height of the table by comparing both measurements and coming to the conclusion the table was a bit smaller than the first one by roughly 20 centimetres ?

[@Spyx84]

1:51 *Now notice the height from the top of the cat at the botten to the top of the cat at the top* This is so catchy!

[@therash09]

Just stack one arrangement above the other; the given dimensions will add up to give the height of two such tables stacked, giving 150 has the height of one table. Approaching a problem visually is more satisfying than applying equations!!! 😊 EDIT: Oh, you mentioned the visual method as well in your video!!! I was not expecting this to be there!!!

[@ulbudhiya7360]

Let, Table = T ; Cat = C ; Turtle = TU According to the question, T + C - TU = 170 cm. . . . . . . . . . ( i ) T + TU - C = 130 cm . . . . . . . . . ( ii ) Add equation ( i ) and ( ii ), we get :- 2T = 300 cm or, T = 150 cm

[@marsbars1105]

An interesting way of solving this is noticing that picture 2 shows the inverse of operations imposed on image 1. So you can just find the average height of the two: (170 + 130) / 2 = 150cm This abstracts away the algebra involved so no cancelling of terms is necessary.

[@traveling_kat]

I got stuck just solving for the cat and the turtle, when I only needed to figure out the height of the table

[@miyaj6104]

You can also find cat and turtle height

[@Itsrubinz]

@@miyaj6104 how please

[@javiersanchez5443]

There are no fixed heights for them. They are whatever that fits with cat - turtle = 20. It could be 60 and 40, or 30 and 10, etc

[@Retinetin]

My Engineer brain thought "Two Equations, 3 Unknowns, unsolvable" I'm continually blown away how becoming smarter can make you less smart in some ways

[@LuisHernandez-dn4rh]

same thought process here 😂

[@mariokajin]

Yeah but you have to solve just one. And two of the “variables” are to be discarded. Be an engineer, find ways trough use looong shortcuts etc. I design roads, parking lots, storm water lines…. Not structural but still engineering.

[@TremereKorbu]

@@mariokajin solving a system of 6 linear equations brings us height of table = 150 cm, height of turtle = 10 cm and height of a cat = 30 cm.

[@petersilie2432]

Solved it by trial and re-try. Tested for different heights of animals and eventually found that the animals' heights must differ by 20cm. From there the only fitting height of the table was 150cm.

[@Inspirator_AG112]

c + x - t = 170 t + x - c = 130 This is two-equation algebra. c + x - t + t + x - c = 300 c - c + x + x - t + t = 300 2x = 300 *x = 150* _Averaging the measures would also get one here._

[@nezamasarie4543]

One of the few problems of yours i solved My sol was setting it up as an algebraic problem using variables x,y,z to represent the cat,turtle and table respectively x+z-y=170 y+z-x=130 adding the 2 gives 2z=300 dividing 2 from both sides gives z=150 which is the height of table

[@pieropurich990]

please, help me in understanding what's wrong in my reasonement: turtle is X, cat is Y, table is Z: so 2Z+x+y=300 That means that, if the solution of the video is right (table is 150), cat and turtle are 0 cm high. I can't understand what's is wrong in my idea.

[@pieropurich990]

please, help me in understanding what's wrong in my reasonement: turtle is X, cat is Y, table is Z: so 2Z+x+y=300 That means that, if the solution of the video is right (table is 150), cat and turtle are 0 cm high. I can't understand what's is wrong in my idea.

[@pieropurich990]

please, help me in understanding what's wrong in my reasonement: cat is x, table is y. So x+y=170 table is y, turtle is z. So y+z = 130 so 2y+x+y is 300 But, if the solution of the video is right (table is 150), cat and turtle are both 0 cm high. I can't understand what's is wrong in my idea. Please, help me!

[@NLTops]

I figured it out through pure intuition because you said it was an elementary school problem. 😆 At that point I just had to look at the elements and notice the pattern. It's asking for a specific height so the numbers are obviously the starting point. The cat and turtle swapping positions leads to the difference between the two numbers, and that is the only relationship between the numbers. That difference is 40 so add 20 to the lower number, 150.

[@denusklausen3685]

because you only need two: x - y = 170 cm y - x = 130 cm y = 130 + x x - 130 + x = 170 x + x = 300 2x = 300 x = 150 somehow as long as 130 and 170 are added together on one side of the equation, then it will work out.

[@paulke1859]

@@denusklausen3685 You should recheck your equations. If you were to substitute the x into your equation, x and y don't match up.

[@denusklausen3685]

@@paulke1859 it does add up, 170 should be -170, but it isn't a matter of algebra but of relations. It is a problem of logic. There would be no need to show the right equation, all I am showing here is that the relation between 130 and 170 is such that it naturally suggests 150 as the answer.

[@ahotbanana]

Got the right answer in a much more round-about algebraic way. I subtracted the 130 height equation from the 170 height one to remote the table height instead of spotting that things would cancel out from adding them. Got there in the end at least

[@jakubkrcma]

For those who find it difficult to understand: Table = x, cat = y, turtle = z First case: x + y - z = 170 Second case: x - y + z = 130 The table height in the first case: x = 170 - y + z The table height in the second case: x = 130 + y - z The table height is equal in both cases (x = x), therefore: 170 - y + z = 130 + y - z Now express the height of the cat (y): - y - y = 130 - z - 170 - z -2y = -40 - 2z 2y = 40 + 2z y = 20 + z Now put the height of the cat into the first case equation: x + (20 + z) - z = 170 x + 20 + z - z = 170 x + 20 = 170 x = 170 - 20 x = 150 *The table is 150 cm tall.* Checking the result using the second case equation: x - (20 + z) + z = 130 x - 20 - z + z = 130 x - 20 = 130 x = 130 + 20 x = 150 *The result is verified.*

[@frogsecretaryofswamp452]

elementary kids doing algebra

[@jakubkrcma]

@@frogsecretaryofswamp452 Yep. Still, some people in the comments had trouble with it.

[@jakubkrcma]

@Fly Oz 🤣🤣🤣

[@pslalithadevi2095]

Good skill

[@GeezSus]

Did exactly this lol

[@trevcam6892]

The expression minus C plus T is common to each equation so it is just a case of substituting -C+T to get the answer without even needing to know what C and T are. The question doesn't ask what C and T are anyway. 150 cm.

[@handdog3]

Something that is maybe interesting (or maybe I did it wrong). I used Algebra, but I formulated different equations than you did in the answer. I wrote (for the left-hand drawing) that the Table Height = Turtle Height + 170 - Cat Height. And then for the right-hand drawing, I wrote Table Height = Cat Height + 130 - Turtle Height. Then I solved the equation: Turtle Height + 170 - Cat Height = Cat Height + 130 - Turtle Height. The answer is Turtle Height = 2 (Cat Height) - 40. Then I substituted that answer for Turtle Height in the earlier equation, so I had: 2 (Cat Height) - 40 + 170 - Cat Height = Cat Height + 130 - (2 Cat Height - 40). That works out to Cat Height = 20. Then I plugged that value into the earlier result that Turtle Height = 2 (Cat Height) - 40. Although I got the seemingly incorrect result that the Turtle Height = 0, when I plugged the values for Cat Height, which was 20, and Turtle Height, which was 0, into either of my original equations for the Table Height, I ended up wit the correct result of the Table Height being 150 (seen here: Table Height = Turtle Height (expressed as 0) + 170 - Cat Height (expressed as 20)... or TH = 0 + 170 - 20...or TH = 150). So my question: Did I do something wrong or is the turtle's height actually 0?

[@wundermax1993]

well, I had the same issue, tried to see the height of the cat or the turtle. Bad at math so obviously the only thing I know is that the cat is 20 cm taller than the turtle. I have no idea how to formulate the fact that we cannot know the exact numbers using algebra, but yes 0 cm turtle height works fine :) I wish I had a mathematician on a shelf here so that I could ask for explanation on this.

[@txorimorea3869]

@@wundermax1993 Is a free variable, you need more information to know the height of the cat and the turtle. You can as well have a turtle with negative height or even multidimensional and the math will still work.

[@wundermax1993]

@@txorimorea3869 now I need to know how to set this up to calculate all 3 values :D I guess you will need more equations for that.

[@Borgozable]

I solved it visually in a slightly different way: overlapping the two images clearly shows that the turtle is 20cm and cat 40cm.

[@thebigmacd]

Actually, the height of either animal is not able to be calculated. All that is known once the solution is found is that the cat is 20cm taller than the turtle. They cat could be 160cm tall and the turtle 140cm tall. You can't assume diagrams are to scale unless stated.

[@Schyshy]

Yes but it works nonetheless. The cat must be 20cm than the turtle because from the left picture to the right one it loses 40cm because of the height difference between cat and turtle 20 twice. So the cat must be 20cm taller. Now replacing the turtle on the left picture with a cat, we have a height of 150cm, since we have to subtract the 20cm from the height difference. Now 150 is the height of the table, since both cats are equally tall and therefore can be subtracted from the equations. At least that's how my solution was

[@jayvanblaak347]

@@thebigmacd It actually is! :) The height of the cat equals to 24,4.. and the height of the turtle equals to 4,4... To confirm: 24,4-4,4=20 170-20=150 and 130+20=150. If anybody still wants this worked out I can post it here, worked it out on paper.

[@rrsharizam]

Luckily this question only ask the height of the table, not cat or turtle. Otherwise, it would be unsolvable. You have 3 unknowns but only 2 equations. You won't solve the height of the other two

[@Mrz8723]

Cat is 40cm, turtle is 20

[@John_Chakder]

It can be anything as long as the difference(cat-turtle) is 20 cm

[@janisstrazdins3367]

Cat=30, turtle=10 :)

[@nissi477]

Your Solution room is a line

[@falsusficta3488]

Damn I was trying to solve it visually when my brain went “Ah it’s probably just a visual aid for the math problem, it probably isn’t one to one with the actual scale just try the math you’re bad at instead.”

[@wardasz]

I've done it diferently, but also artmeticly. For clarity - T is table, c is cat, t is turtle I started with basic equasions you had, but I change them to be about table: T = 170 - t + c T = 130 + t - c Than i can merge them together, and than bring all the unknown to one side 170 - t + c = 130 + t - c 170 = 130 +2t - 2c 40 = 2(t-c) t - c = 20 And with (t-c) calculated, I can just drop it into the one of the main equasion, and have a solution. T = 170 - 20 = 130 + 20 Simple and basic method, I probably forgot all the more advanced one since I graduate :D

[@kokodin5895]

i solved it i a bit convoluted way table = cat +130 - turtle and table = turtle +170 - cat and since they both equal table we can substitute one table with the other equation we get some monster like cat + 65 = turtle + 85 therefore cat = turtle + 20 we go back to the first two equation and substitute every cat with turtle + 20, turtles cancel each other out and we get simple table equal 130+20 or 170-20 and they both 150

[@danser_theplayer01]

I almost solved it visually, I thought it was 140.

[@dakota_dll]

2:09 yes I can VERY CLEARLY VISUALISE THIS

[@gimmiedashasha]

You could just look at it and see it's 150cm i'm sure most people solved it like that.

[@plasmaearth1796]

bro how

[@StormAn1mal]

i found option 3 by imagining an generic y-axis. my table has a height of 5 units. on the ground (y=0) i have a box with height of 1 unit. on the table i have a box with height of 2 units. y1 y7 = 6. now i switch the boxes and it's y2 y6 = 4. the average of these distances is 5, the height of my table. tested with bigger boxes and other heights of the tablet and results were always the same. so it's (130 + 170) : 2 = 150 for this logic test.

[@edwardgoodson7628]

I solved it with a third method. The difference in the two heights was 40 cm. The turtle was shorter than the cat so the difference in their heights was added to the table in one case (+ Cat - turtle) and subtracted from the other case (- cat + turtle) so you could add half the difference to the shorter or subtract it from the taller either gave 150cm

[@rgazsy8366]

My algebra was a bit more convoluted figuring that the cat was 20 cm larger than the turtle. Turns out it was a longer way of doing the same thing

[@antoniomachado4005]

How do you know how tall is the cat ?

[@tibfulv]

Antonio Machado We don't. But it isn't necessary to figure out.

[@rgazsy8366]

Antonio Machado I figured the DIFFERENCE between their heights, not their heights.

[@martinhartecfc]

I used the simultaneous equations method with the thumbnail and was feeling pretty good that I remembered how to do that 20 years after studying it in school. Then I watched the video and you took the wind right out of my sails by saying kids in China do this in elementary school! I was about 15 when we studied simultaneous equations at school. I could never have solved this in elementary school ha ha! The visual proof was cool too. It didn't occur to me and it's quite pretty.

[@mysteryman7877]

Here’s a third method: Going from 130cm to 170cm requires adding the height of the cat and subtracting the height of the turtle twice (once on each side of the ruler). That makes a different of 40/2 = 20cm height between the animals. Substitute one for the other and you have 150cm height, which can just be translated down to the table with no scaling.

[@NoNameX_X0]

that’s the way i did it too.

[@madhusudansingh9925]

It's easy. Assume table hight = x; cat hight = y; tortoise hight = z Given; x+y-z = 170 x-y+z = 130 adding both equations and deciding by 2 x = 300/2 = 150cm = table hight.

[@Jim-tv2tk]

Proud of myself for solving an elementary school math question :) Been awhile. Paused at 0:13. Now I'm going to watch the rest of the video to see how I did.

[@stevez6460]

I did 170+130 to get the height of 2 tables stacked on top of one another then divided by 2.

[@RE5MGS4fans]

in a minute I solved it simultaneously with x+c-t = 170 and x+t-c = 130, seems easy but...explaining it to your child at primary school in a lucid way without using any algebra is, however, no easy task at all

[@warrior100girl]

RE5MGS4fans in china you learn this in 2nd grade primary school.

[@Bombfun]

YES, you see the problems. I am Hongkonger, such math problem is common in Hong Kong. It is just a P2 or P3 math problems. you cannot use algebra. you just can use simple method to solve it and explain it to child. I know algebra is easy to solve. Nearly all of the solution here can't see the major problem.

[@Tehom1]

Thanks for the puzzle, Presh. 170 cm = the table's height T + the cat's height C - the turtle's height U 130 cm = T - C + U so (170 + 130) = 2T T = 150 Don't want to be a math meanie, but, well, I spent 5% of the time on this puzzle and 95% thinking how to gently phrase the suggestion that this puzzle doesn't have a twist.

[@brosephproseph1741]

OMG I used the same letters as you did to solve this problem. wow

[@brosephproseph1741]

I'm guessing you picked U for turtle because you realized you couldn't use T huh?

[@Tehom1]

Yes, exactly. Lucky the little one wasn't (Ancient Egyptian Pharoah) Tut, or I'd be out of letters.

[@aeromodeller1]

Oh, but there is a twist. Solving two equations with three variables?

[@brosephproseph1741]

@@aeromodeller1 yes, you can do that if variables cancel out

[@Hennu_TRM]

I figured out the difference in height between the two animals is 20cm. The difference between the measurements 170cm and 130cm is 40cm, but you can see the way it's set up the difference is taken off of both sides of the measurement, or that's how I would say it. When you know the cat is 20cm taller you can pretty easily imagine a situation where you measure from a cat on the floor to a cat on the table which would require subtracting 20cm from the first measurement, showing the table is 150cm.

[@acool6401]

Two animals interchange positions depending if they were at table 1 or table 2, therefore any difference in distance between the two dimensions is obviously due to just swapping their positions therefore making the 40 cm difference between the two dimensions divisible by two (since there are two tables) in order to effectively eliminate the animals from the picture altogether. This invariably means that 20cm must be added to the shorter dimension and 20cm must be subtracted from the bigger dimension in order to arrive at the same measurement for both tables since both tables must be the same height.

[@timoriusmaximus]

Okay I overcomplicated it. I made other equations for each picture: 1. Cat + X = 170 2. Turtle + Y = 130 And then thought how to add things for each picture to get the hight of the table: 3. Table = Y + Cat 4. Table = X + Turtle I rearranged the 1..and 2. equation to the animals and put 1 in 3 and 2 in 4. I ended up with x-y = 20 what I was able to put in one of the rearranged equaions to get Table = 150. Yeah I know its very complicated but its middle of thr night for me... :3

[@technoultimategaming2999]

Same here. I got every possible way to get X (table) X=c+a a=(distance from cat on floor to table) X=t+b b=distance from turtle on floor to table) Z= C+b+t z=(total height when cat on table) Y= C+a+t y=( total height when turtle on top) X= t-y X=c-z D= c+t (what I thought about is flipping the cat/ turtle upside down) I relised it kept a and b same so X= D-C-B X=D-T-A C=t-a T=c-a

[@suruchiagrawal6230]

I solved it similarly.

[@dnomyarnostaw]

That was my method as well. So many ways of thinking.

[@discovaria9507]

Isn't cat at the top?

[@CerberusDawg]

I just divided the difference (40) by 2 (20) and added it back to the lower number (130 + 20)

[@davidbeck9066]

The funny thing is I dont think we actually know the height of the cat and turtle until we work out the height of the table, only the difference. I thought they were 40 and 20 and used those numbers at first.

[@aleksandrneprimerov278]

I tried calculating those for an hour and failed miserably lol. Yes they are 40 and 20, but my primitive methods are clearly not enough to properly deduce them. Correction - different heights are possible

[@blindvi4849]

I got the height of the turtle visually immediately, then calculated the height of the table knowing the cat was 2 turtles height and the turtle was 20cm

[@grassfedbutter]

The real height of the turtle and cat doesn’t matter at all. C=t+20, so you can pick any reasonable number with a 20cm difference and it doesn’t have to be 20cm and 40cm. I personally think for the sake of reality, 30cm and 10cm probably makes the most sense.

[@davidbeck9066]

@@grassfedbutter Once you finish the table height you can go back and find out that the Cat is 30cm and the turtle is 10cm

[@maxbl5683]

@@davidbeck9066 You don't know the relationship between the cat and the turle (ignoring the picture given). The only thing you know is that the difference between their heights is 20 cm.

[@iAmGGlitch]

What I Did: Cat + Table - Turtle = 170 Turtle + Table - Cat = 130 170 - 130 = 40 For Difference Between Images Since the difference is affected equally by both sides, 40 / 2 = 20 170 - 20 = 150 130 + 20 = 150 Ans = 150

[@benbever4061]

I calculated it a hard way. 170+turtle+turtle= 130+cat+cat. So cat+cat is 40 more, so cat is 20 more than turtle. Table+cat-turtle=170 and table+turtle-cat=130, so table+20=130 and table-20=170, table=150.