Can you ace this interview puzzle?

This is a fun interview riddle from Math StackExchange.
math.stackexchange.com/questi...
Subscribe: kzbin.info...
Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas!
If you purchase through these links, I may be compensated for purchases made on Amazon. As an Amazon Associate I earn from qualifying purchases. This does not affect the price you pay.
If you purchase through these links, I may be compensated for purchases made on Amazon. As an Amazon Associate I earn from qualifying purchases. This does not affect the price you pay.
Book ratings are from January 2023.
My Books (worldwide links)
mindyourdecisions.com/blog/my...
My Books (US links)
Mind Your Decisions: Five Book Compilation
amzn.to/2pbJ4wR
A collection of 5 books:
"The Joy of Game Theory" rated 4.3/5 stars on 290 reviews
amzn.to/1uQvA20
"The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" rated 4.1/5 stars on 33 reviews
amzn.to/1o3FaAg
"40 Paradoxes in Logic, Probability, and Game Theory" rated 4.2/5 stars on 54 reviews
amzn.to/1LOCI4U
"The Best Mental Math Tricks" rated 4.3/5 stars on 116 reviews
amzn.to/18maAdo
"Multiply Numbers By Drawing Lines" rated 4.4/5 stars on 37 reviews
amzn.to/XRm7M4
Mind Your Puzzles: Collection Of Volumes 1 To 3
amzn.to/2mMdrJr
A collection of 3 books:
"Math Puzzles Volume 1" rated 4.4/5 stars on 112 reviews
amzn.to/1GhUUSH
"Math Puzzles Volume 2" rated 4.2/5 stars on 33 reviews
amzn.to/1NKbyCs
"Math Puzzles Volume 3" rated 4.2/5 stars on 29 reviews
amzn.to/1NKbGlp
2017 Shorty Awards Nominee. Mind Your Decisions was nominated in the STEM category (Science, Technology, Engineering, and Math) along with eventual winner Bill Nye; finalists Adam Savage, Dr. Sandra Lee, Simone Giertz, Tim Peake, Unbox Therapy; and other nominees Elon Musk, Gizmoslip, Hope Jahren, Life Noggin, and Nerdwriter.
My Blog
mindyourdecisions.com/blog/
Twitter
/ preshtalwalkar
Instagram
/ preshtalwalkar
Merch
teespring.com/stores/mind-you...
Patreon
/ mindyourdecisions
Press
mindyourdecisions.com/blog/press

[@anuragguptamr.i.i.t.2329]

According to Newton's forward interpolation formula, the answer should be 208. Here is the formula created (where, simply b=a+1): f(a,b) = 8 + 42*(a-3) - 31*(a-4)*(b-4) + (101*(a-4)*(b-4)*(a-5)/6).

[@MindYourDecisions]

This simplifies to the cubic equation f(a) = (101 a^3 - 1398 a^2 + 6301 a - 9000)/6 and indeed f(7) = 208. This is quite interesting, thanks!

[@mykal4779]

wow it actually works for every term. so there's a systematic way to solve these kinds of problems?!

[@anuragguptamr.i.i.t.2329]

@@mykal4779 Yes, thanks to Newton and Lagrange.

[@anuragguptamr.i.i.t.2329]

@@MindYourDecisions Welcome Sir. You're an amazing Mathematician!

[@_catzee]

@@anuragguptamr.i.i.t.2329 I always thought there was probably a cool way to determine a non-piecewise function containing any set of points (as long as it's possible to pass the Vertical Line Test with that set of points). Is Newton's forward interpolation formula that "cool way"?

[@onealwang2363]

Guess I'm not getting a job any time soon

[@brunogianardo4553]

me neither...

[@user-bh1hn5gy5y]

You sure will.

[@user-bh1hn5gy5y]

You sure will.

[@DeSlagen8]

Getting a job is easy if you’re not a pushover

[@markstephensondds270]

I'm guessing that this was not on any interview, anywhere, ever.

[@Eduarodi]

What job did they offer? As a lawyer? I mean, if you can convince anyone that the answer is 224, you can win any case.

[@pqsk]

Could be an engineer job. I’ve had some weird questions in interviews, but usually it’s related to real math/computer science problems.

[@Eduarodi]

@pqsk I really hope engineers stick to conventional maths calculations and proven results. The same goes for doctors, architects, and anyone you depend on for your life.

[@pqsk]

@@Eduarodi it’s problem solving. It’s the same with some computer science problems. It’s not about the solution, but how you came to the solution.

[@Eduarodi]

@pqsk Yes, I understand that and in a way I was joking. I'm "only" an English teacher, and I didn't think that creativity played a role in that kind of jobs.

[@pqsk]

@@Eduarodi it does and sadly many junior devs just memorize algorithms and don’t understand them well enough to dissect them and come up with their own solution. So when they ask a problem that’s the same they sometimes don’t see it because they just memorized it instead of understanding it

[@ChannelJeffrey]

If this really was an interview, I would say "7×8 is 56, the four people that answered Before me, are wrong, that's obviously why you're looking for new employees"

[@kojistaakter4991]

5×6=30, that's right..

[@prufrock1977]

I was thinking something similar, “because I don’t have time to see a clear pattern (it’s an interview after all), I can only guess that three of these are incorrect, and one of the is correct. And the answer to 7x8 is 56…”

[@Kirkemus]

COOL! And SO true!

[@ChannelJeffrey]

Good point about 5x6. I still think I'm the bet applicant

[@SpruceOaks]

Yes, that is exactly how to answer this question.

[@roysreceptive]

“Congratulations, you got the job. Now, remember the boss takes his coffee with two creams and no sugar and all in-coming calls can reach him through line 4.”

[@bryanCJC2105]

"I'm here for the dog walking job. Just what kind of dogs are these?"

[@JackPullen-Paradox]

Doberman Integers.

[@rollnstone5539]

the answer is 56. 4 incorrect answers don't change that. moving on

[@christologian1518]

This is what the interviewer was looking for. Yours is the correct answer (which will be lost on all those who can read math and simultaneously miss the point of the very question they're reading). If this comment section is the interview, you got yourself hired and the vast majority missed it. The interview question is genius

[@kespeth2]

ACtually, 3 incorrect answers. 6 * 5 is indeed 30.

[@markmurto]

Answer could be any multiple of 8.

[@CheryPet93]

@@christologian1518not if the interview is for a job, where you need to find patterns and/or solutions to problems that need a logical aproach (in a mathematical sense) like a job as mathematician 😊

[@rollnstone5539]

@@kespeth2 yet another example of my mouth getting out ahead of my brain

[@calholli]

This is exactly how theoretical physicists work.. Lets assume that random 2 is a pattern; then lets assume it has to be a positive integer.. Lets just keep stacking assumptions on top of each other until we feel like quitting.

[@artemisfowl7307]

Not rxactly

[@recang360]

Let's assume the upper reply is an assumption

[@robair67]

Pretty accurate observation. They go one step further by stacking their own assumptions on top of those of previous theoretical physicists, who also balanced their ones on top of even earlier theoretical physicists. And when limit conditions throw out infinities, they add more assumptions to get rid of them. And society holds them up as geniuses! And God just smiles down on His Creation!

[@artemisfowl7307]

@@robair67?

[@j.r.1210]

"Insane Interview Riddle" is actually a good title for this post. What I find mind-boggling is the notion that this kind of question makes for an effective job interview -- for any position. This is not a "see how they think" question; it's a "watch 'em squirm" question. But job interviews as defined by KZbin logic/math channels apparently have little to do with identifying hirable skills. It's a weird, "gotcha" landscape.

[@galois6569]

It is to test that you can approach difficult problems and what you do when there is not a proper solution. The interviewer doesn't care if you get the same answer they did, they want to see how you think.

[@txorimorea3869]

Not at all. People at the interview stage already have the hire-able skills, but is hard to know how they will behave once they start working. There is a lot of information one can get from a person doing such riddles. Real life problems can't be solved just following a recipe, some people can't handle stress, others give up easily, some are bad at dealing with frustration, others can't communicate, etc.

[@squee222]

That's HR for ya...

[@squee222]

@@galois6569 They want an excuse to hire and fire based on biases and preconceptions. Open ended question with an open ended answer also gives HR the freedom to make open ended decisions which obfuscate the real reason someone did or did not get a job.

[@konstantin.v]

​​@@galois6569, this problem isn't _difficult,_ it's idiotic 🤬

[@kennethforeman6164]

Since this is a finite length series, the next element can be any number you chose. The challenge is in finding what function justifies that choice. For example, the axb could merely be the x and y coordinates, with functional output being the height. Pick any height at 7x8. Alternatively, we could say that this series is mathematical only. Let (a+b+1) and the answer have a varible multiplier. The multiplier series starts with 1(8/8), 5(50/10), 2.5(30/12), 3.5(49/14) for the given data. Assume the multiplier series is composed of alternating terms of two subseries with those terms related by either addition or subtraction. Then the multiplier series extends as 1, 5, 2.5, 3.5, 4, 2, 5.5,0.5,... Hence 7x8 is still 224 but 8x9 is 144 rather than 108 by the pattern found in the video. Without significantly more context, the answer could be anything... The question is more intended to pull out your biases and prior experience, not your ability to find "the" right answer.

[@ichigonixsun]

Since no restrictions are given whatsoever, you don't even need to think very hard to find a function that justifies your choice. Just define it piecewise.

[@tarajoyce3598]

Great. I chose 7 😂

[@user-cs8zw6xi6k]

I hate such tasks. You can come up with an infinite number of rules that satisfy the given examples.

[@manusarda]

Ok. Leave infinite. Just give me 3-4 rules Because I failed to find even one.

[@geoemg7140]

A little correction, 1) you hate what you can't solve 2) there might be infinite rules, but you cannot come up with any of them. Just take the L and move one mate

[@arolimarcellinus8541]

I mean like who even think that it involves gcd() function?? It didn't even specified in the problem. Only the geeks one that can solve it

[@randomgamer-te8op]

​@@geoemg7140 so you must be that one guy that actualy solved it and went to the comments merely to brag about it

[@geoemg7140]

@@randomgamer-te8op nah i didn't, im just not salty

[@patrickarmstrong8908]

Basically... you got lucky in guessing that one of the numbers was squared, rather than a log, or a fourier transform of a Huffman compression of "War and Peace."

[@christologian1518]

56. The interviewer is testing us. If a man say, "all dogs have five legs", then he asks me how many legs a dog has, the answer is 4. It's not a trick question. It's a test. That's why it works as an interview question, because it shows how a person thinks.

[@galois6569]

always my first thought on such questions.

[@deathstroke872]

What if it is an amputee dog or an extraterrestrial dog.

[@carultch]

@@deathstroke872 An extraterrestrial dog wouldn't even be a dog by strict definition, since it would be another species entirely, so that's a moot point. A dog who was amputated was still born with the DNA to make 4 legs, and would have 4 legs if there wasn't an accident or disease that led to the amputation. If you clone an amputated dog with 3 legs, the clone will have 4 legs.

[@indigoziona]

THERE ARE FOUR LEGS /picard

[@huzefa6421]

Thats Trua though Ngl

[@WhiteGandalfs]

Since the whole problem has far more degrees of freedom than the presented stipulation, the number of constructions (with literally ANY function whatsoever) that would yield ANY result fitting the presented values could be counted as "infinite". Under those infinity multitude of constructable functions yielding results that satisfy the four presented "result" numbers together with the presented "input" can be ANY amount of instances that as well satisfy the undisclosed result "224" - as well as infinitely more ones that deliver ANY other fifth number. The takeaway of that nonsense is that the person who made that thing he calls "riddle" has a serious deficit in understanding the principle of "degrees of freedom of systems". I would suggest to strictly avoid entering business partnership with people being at that level of naivety.

[@GandalfTheWise0002]

Pretty much my reaction as well. Though I might play a few games with it to get a read on the people in the room. I'd might make a big show of doing a simple polynomial fit of f(3)=8, f(4) =50, etc. and f(7)=X, and then ask what they'd like X to be, or maybe say that I like pi and let X=pi. Their reaction would tell me a lot about what kind of place that would be to work.

[@michaelawilliams]

My advice: if you get asked an interview question like this, "What is 7 x 8 ?" the best answer is "What do you want it to be?" I would hire that candidate very time. ;-)

[@756jrs]

You'd be a horrible person to work for if you are just looking for someone to please your whims rather than someone who will analyse and solve the company's problems.

[@rogerkearns8094]

_What do you want it to be?_ A good response to give if you're being hired as someone's accountant. ;)

[@drziggyabdelmalak1439]

Brilliant! I like it!

[@semiconnerd]

Works with a Newton interpolynominal, (4th order polynominal). If you use a 3rd order polynominal the result will be 208.

[@nathanmays7926]

I really dislike the multiplication and equal signs in these riddles. Should be function of or something.

[@carultch]

Exactly. Should use a symbol that doesn't already have an assigned purpose, if you are using it for an operation you made up. Like a club symbol from a deck of cards.

[@squee222]

I did the multiplications on the left. Considered the equals sign to be an abstract transformation. Graphed the values on two axis. Called the 4*5=2050 data point an outlier as the other three points can be linearized. Determined the slope between each points to be 1.22, and 1.58. Averaged these to determine the final data point to be approximately 69. 69 final answer!

[@coski87]

Nice

[@thatsmykulture7266]

Hahaha 69 (said in a billy madison voice)

[@Vizz111]

Nice

[@ashyourresidentenby5916]

I noticed that each of the "products" (8, 50, etc.) are multiples of the second number (which you called b). so I divided each of the products by b and I got 2, 10, 5, and 7. I noticed that each pair added to 12 and that the first number in the second pair was 3 more than that of the first pair, so according to this pattern the first number in the third pair would be 8, making 7 and 8's "product" 64 (8 times 8)

[@troybingham6426]

Wow good thinking. That's a better pattern than the one he found in the video.

[@markdaniel8740]

What pairs are you referring to?

[@Nicks721]

@@markdaniel8740 2-10,5-7

[@ZackBlackwood97]

What pairs?

[@Nicks721]

@@ZackBlackwood97 2-10, 5-7

[@toomanyhobbies2011]

How odd. I had an interview with an arrogant jerk. All he did was talk about himself and propose the oddest questions, like this one. I think he just wanted to show how smart he was to someone with degrees. The other interviewers actually said this about him. Unfortunately it was the jerk that chose the final candidate. When I got the call that I wasn't getting the position, I said "thank you, I couldn't have worked with that guy anyway". The bearer of bad news agreed, because he couldn't stand him either.

[@leif1075]

May i ask what type of job it was and what that person did for a living besides interview ppl?

[@elijahkropf]

The first thing I noticed was that each solution is divisible by the second number (in spite of "×" not meaning anything). 8/4=2, 50/5=10, 30/6=5, and 49/7=7. I then tried to find a pattern among the numbers 2, 10, 5, and 7. 7=2+5, so I simply stipulated that n = n_-3 + n_-1. Following this pattern, the next multiplier of 8 would be 10+7=17. 17×8=136, so that was my answer. Unfortunately, it failed to include the first number in the equation. But in my opinion, if it's truly open-ended, the linear sequences 3-7 and 4-8 are less critical than the nonlinear solutions. If all symbols are arbitrary, this could be a solution for a: a = b-1, where b and c have that relationship I described. I suppose my formula would be: c = b × (c_-1/b_-1 + c_-3/b_-3)

[@selfishvirtue28]

Lol

[@Renslay]

According to my calculations, it's 208. The sequence "n times m" has only one parameter, since m=n+1 (at least that is what is given to us). So we can actually ignore m. And we see consecutive inputs for n=3, 4, 5, 6. So we can refrain the question: What comes next in the sequence 8, 50, 30, 49? I agree with the comments "the answer can be anything". Watch Mathologer's video "Why don't they teach Newton's calculus of 'What comes next?'" if you want to see how to create a function for any sequence! I just do the steps they mention in the video: Original input numbers: 8, 50, 30, 49 First order differences (differences between consecutive inputs): 42, -20, 19 Second order differences (repeat the same): -62, 39 Third order differences (repeat the same): 101 This defines us a possible function of f(n) as: f(n) = 8*(n chose 0) + 42*(n chose 1) - 62*(n chose 2) + 101*(n chose 3) where the coefficients are the first elements of each sequence. Rephrasing f(n) we get: f(n) = 101n^3 / 6 - 163n^2 / 2 + 320n / 3 + 8 This function fits on the given inputs. Let's see if we are correct: f(0) = 8 f(1) = 50 f(2) = 30 f(3) = 49 And if we go one step further: f(4) = 208 The answer is 208. If you don't like that we start at 0, we can define: x "times" x+1 = f(X-3). And of course, you can use an infinite number of other functions that does the trick!

[@Renslay]

If I want f(4) to be 224, I can calculate a new f(n) function based on that data: Difference-pyramid: 8, 50, 30, 49, 224 42, -20, 19, 175 -62, 39, 156 101, 117 16 From the first elements, we have: f(n) = 8*(n chose 0) + 42*(n chose 1) - 62*(n chose 2) + 101*(n chose 3) + 16*(n chose 4) In a different form: f(n) = (2 n^4)/3 + (77 n^3)/6 - (445 n^2)/6 + (308 n)/3 + 8 Testing: f(0) = 8 f(1) = 50 f(2) = 30 f(3) = 49 f(4) = 224

[@selfishvirtue28]

Lol

[@thebitterfig9903]

My main conceptual problem with a lot of these is that similar problems often use familiar mathematical notation. If they just stuck in an “&” instead of an “X” I’d appreciate it more. Heck, I’d appreciate the original folks asking the riddle more, since there’s a level of fast and loose with mathematical grammar that I would prefer not to work for.

[@giladkay3761]

I always just convert it into a function f(3,4) = 8 ... f(7,8) = ?

[@lawrencejelsma8118]

​@@giladkay3761... That is extreme. The KZbin presenter changed the x to the proper abstract algebra way of saying "math operation in products (and maybe additions)" operator notation of a circle around the "x" symbol. In electrical circuits it is the same symbol in "mixer circuits" adding to an input signal. It is also a "mixed feedback" notation of adding or multiplying the input signal commonly seen in Operational Amplifier circuits.

[@ThisCanBePronounced]

except.... many people do use x for and in some places, so it could be justified! Oh no! :D

[@wohlrajh666]

The issue with the symbol he chose is that it often implies that it is commutative, which is actually not even true in this example. @@lawrencejelsma8118

[@lupus.andron.exhaustus]

If this was a real question in a job interview, the only correct answer would be: "It's as much as your lawyers say it is. And if it isn't, you need better lawyers!"

[@bucc5207]

The correct answer is, "I'm not playing this game. Thanks for showing me what working here would be like."

[@GaganMaheshwari0]

I think this is unnecessarily over-complicated. I mean, consider this random function I thought of: f(a, b) = (a mod b) ^ LCM(a, b) * a^2 + b^3. Who'd be able to guess this easily? Honestly, I like your videos Presh, but don't just pick anything available. I therefore, prefer the puzzles on Numberphile. They're more intriguing and engaging.

[@JackPullen-Paradox]

I would say that it would be important for some employers to know if your problem-solving technique involves a lot of random guessing, or if you are able to cobble together on the spot a rational or creative approach to discover the solution to a problem. It would be more like, can your technique find the solution or discover reliably that there is no accessible solution in a reasonable timeframe, Using such problems, the employer could possibly gauge tenacity, flexibility, creativity, and general skill.

[@evalaviniabucur1789]

I thought about 64 - that being because I replaced the series 3, 4, 5, 6, 7 (formed by adding 1 to the last item) with the series 2, 10, 5, 7, 8... (4, 11, 1, 14, -2 etc) (formed by two interlaced series - one starting at 2 and growing by 3 and one starting at 10 and growing by -3). Now I'm not quite sure if I was allowed to do that (and I agree the presented solution makes a little more sense), but mine would still hold in the end, so I ended with 7x8 = 8x8 = 64. The next term would have been 8x9 = 4x9 = 36 and the next one would have been 9x10 = 11x10 = 110 in this case.

[@shahars.2920]

In my opinion there are infinitely many solutions to this problem. For instance, you can take the function (or "product" in this question): f(x,y) = a*x+b*y+c*sin(pi*x/2)+d*sin(pi*y/2). You use the input and get 4 linear equations with 4 variables a,b,c and d. You can inverse the 4x4 matrix and find that a=133.5 b=-103 c=-19.5 and d=31. So in this case the answer is: f(7,8) = 130. Of course you can choose many other functions, but sometimes the 4x4 matrix is singular

[@technorazor976]

I noticed that every result had the second number as a factor. For example: 8 / 4 = 2 50 / 5 = 10 30 / 6 = 5 49 / 7 = 7 The other factor doesn't seem to have any reasonable pattern, unless you split them into two separate sequences, for even/odd terms: 2, 5 and 10, 7 Considering that there's a difference of 3 between those pairs, it may be reasonable to assume that the factors of the first sequence are meant to increase by 3 each time while the other decreases by 3 each time. This means that the final result would be the product of 8 and the next number of the first sequence, which is also 8, resulting in an answer of 64.

[@dr.maheshkumar8543]

Same to same mene bhi ese hi socha😀

[@diandradeeke]

that looks like the best solution. The number is not that big.

[@technorazor976]

@@diandradeeke Thanks! I remember leaving this comment because I felt other answers were too complicated and probably not intended.

[@troybingham6426]

My answer would be 7 X 8 = 56 (Just because you got the first 4 equations wrong doesn't mean I have to do the same.)

[@ZackBlackwood97]

3 equations wrong. 5 × 6 is 30

[@troybingham6426]

@@ZackBlackwood97 Well played. I acknowledge my oversight.

[@lawrencejelsma8118]

​@@troybingham6426... You are correct if you look at the four operator equations and see the example of where one is correct in simply multiplying them. So when you attempt 7 x 8 = ? you are going to write the correct one as the illustration previous showed of one being correct in a multiple choice illustrated example! 😂

[@lox7182]

yeah, as I commented, this question shouldn't have used the multiplication operator and should have instead just started with that circle operator thing

[@I.____.....__...__]

1:40 THANK YOU! I HATE when "maths puzzles" use actual mathematical operators to mean something other than their actual usage. Unless they're intentionally trying to trick and confuse people (which is a real scumbag move, NO teacher should EVER do "trick questions" in school, that's NOT teaching, it's garbage 😒), then they should just use some other non-mathematical symbol, some punctuation or letter or arbitrary mark to denote the mystery operation. (Oh, and I also don't like questions like this that provide too few data samples because it might be possible to come up with multiple valid answers, for example, 4;5 and 6;7 are 50 and 49, so maybe 8;9 is 48, making some sort of function where if the first number is even, the result goes down by one each time, so you have to figure out how the pattern for the ones with an odd first number, how to get from 8 to 30. Similarly, in the latest CaptainSparklez video, Jordan did one of those to "which one [of 4] doesn't belong" puzzle maps and for many of them, there were multiple valid answers.)

[@rohangeorge712]

there are infinite answers to this obviously because u can just say the pattern is u multiply a and b, and then the product can be matched with the output as a function using lagrange interpolation. There are a bunch of functions that work. Here is onefunction that uses the points (12,8), (20,50), (30,30), (42,49): 28x^3/1485 - 18673x^2/11880 + 5381x/132 - 9485/33. After u plug in 56, u get some random number which isnt 224. Never liked questions like these

[@user-wh7jm7sc4k]

But... What if you think about 3 & 4 and not about 12??? 4 & 5 but not 20, 5 & 6, but not 30... You know me? Create a funtion that: f(3)+f(4)=8 and not f(12)=8... You know the diference? PS: Sorry about my HORRIBLE english :P ps2: i wrote the complet idea for a solution about this kind of thinking

[@rohangeorge712]

yea i get what ur saying. my point to this is that this type of question there is so many answers because infinite functions satisfy the conditions. @@user-wh7jm7sc4k

[@ferrousiron7165]

Another simpler way I found to do this was: (3-1)4 = 8 (4+6)5 = 50 (5+0)6 = 30 (6+1)7 = 49 We see a pattern of the smaller (of course, just correlation) numbers of the first 4 terms added with 1,6,0 and -1. Perhaps the 5th term smaller number would be added a -6. So it leads me to believe that "7*8" = (7-6)8 = 8

[@selfishvirtue28]

Lol

[@BradMurray]

Since this is a recoding problem and there are no well-defined rules for the recoding, we first have to choose what symbols are atomic before recoding. It's tempting to assume the numbers are atomic and naturally defined, but they could have any value after recoding. It's tempting (as you've done) to assume also that the operation is atomic and recode it to provide the answer given naturally defined numbers. Personally I would short-circuit problem and choose to see each expression as atomic and that the problem under that condition is insoluble because there's insufficient information as no symbol (being atomic) is derivable from any other. If pressed for a solution I would choose 419 (arbitrarily) as my personal definition of the last symbol and therefore correct since we're just assigning random numbers to symbols. When forced to invent my own rules I probably will. Whether or not I get the job depends a lot on what they wanted to hear. :D

[@habichvergessen9250]

My first answer was 8. This is because I always took the last digit as the real digit. Then we come to the first one. (3-1)*4=8 (4+6)*5=50 (5+0)*6=30 (6+1)*7=49 And then I took the sum of the added numbers (-1)+6+1+x=0 so at the end „nothing is added“ so x=-6. You could also say it’s a sequence of substracting, adding, adding 0/ do nothing which is repeated and in the middle with mirrored numbers. So the last one is (7-6)*8=8 The hole line: (3-1)*4=8 (4+6)*5=50 (5+0)*6=30 (6+1)*7=49 (7-6)*8=8

[@yedire]

I worked out the same answer and this a better pattern than the solution given

[@The_NSeven]

I thought of the same solution, and yeah, this is objectively better

[@kicorse]

Lots of people hating this as an interview question. For a relevant job, it depends how it's asked. If the interviewer says "this is very difficult and we don't expect anyone to solve it without help, but we want to see how you approach it", then it could reveal a lot about the candidate. Do they systematically go through the equations and see how they relate to a simple product? Do they look for a pattern? Do they immediately get disheartened when nothing jumps out? Do they explore other operators besides multiplication? Do they look at common factors? If there is enough time available, they should get the answer with help, and it's a question of how much help. Lots of interviewers won't understand this, though, and just ask it because they think it's clever to make candidates panic. Then it would be a disastrous question. Also, I the think question should contain the 7x8 answer and ask for 8x9. It then becomes plausible that the interviewee might spot the pattern where there are larger numbers when the LHS is not divisible by 3.

[@arolimarcellinus8541]

I mean....people kinda have common sense to include multiplication and division in this one. Include gcd() or maybe lcm()? Not many engineers still remembers such things, even the postgrads ones.

[@kicorse]

@@arolimarcellinus8541 That's kind of the point. Not all work is just about applying things you've learnt, and if you give up the moment you need to go beyond this, you would not be a suitable employee for some jobs. Someone who's never heard of the concept of common factors should still be able to recognise that 4x5 and 7x8 are not divisible by 3, but 2x3, 3x4, 5x6 and 6x7 are.

[@cadfael4598]

Well, I didn’t get 224. However, I did note that you could make two patterns, 8, 30, 52 and 50, 49, 48……. So that’s what I did. I just assumed that since the product of the number pairs was wrong, it was not about the product itself, nor that you needed to devise a formula to address the issue.

[@George4943]

I have never been asked such 'interview' questions (I retired 12/31/1999, haven't worked this millennium). I would have said, "7 x 8 = 56. However, the question gives 3 wrong answers and 1 correct, so anything should do." An interview goes both ways. I would wonder whether I want to work for an organization that thinks this kind of question is appropriate in a job interview. If the interview continued with a verbal instruction to consider 'x' an unknown binary operation and figure out what it was I would say "Oh, that's a different question, the answer to the original still stands. Given the new question I would go back to the person who assigned me the task and ask, 'What is going on here? What is the larger problem?'"

[@JordHaj]

🤓🤓 Uhhm ackchually there are 4 points(assuming that the second argument is one more than the first) so we can fit a cubic to these points and doing so results in f(x) = -1500 + 1050.1667x - 233x^2 + 16.8333x^3(it satisfies f(3) = 8, f(4) = 50 and so on) and plugging in x = 7, which corresponds to 7 × 8, we get approximately 207.989🤓🤓

[@burningdowntheworld]

Instead of replacing the multiplication symbols I swapped out the equal for the only other pattern I could see which is (from top to bottom): - greater than - less than - equal to - less than - greater than Assuming you set the answer to anything less than 56.

[@timothyphung6403]

Just keep it simple, 7x8 is 56

[@greenlantern7959]

56. Don’t be distracted by false information.

[@markn866]

Yes, are you able to see the objective through BS.

[@franklyanogre00000]

ab²÷2 Where a+b is prime, also divide by three. Or... Divide by the factorial of the number of factors (including 1), so 2 or 3 for most low numbers.

[@dj_laundry_list]

I used the math stack exchange to ask what I thought was a relatively simple question, now I have an unproven conjecture that I need to dedicate time to exploring

[@MrMousley]

If that's the kind of question that they are going to ask at the interview then I probably wouldn't want the job anyway.

[@feelfreefpv]

I first went through the answers to look for any pattern. Then I figured the other employees made some mistakes and thought about a polite way to bring it up on our next meeting without pointing fingers to anyone particular so we could find out how to get a more consistent workflow.

[@AdelaeR]

You're hired.

[@_catzee]

I came up with 7(x)8=8. I saw that if you take away or add something to a, you can multiply it by b to get the result. (3-1)x4=8, (4+6)x5=50, (5+0)x6=30, (6+1)x7=49. I saw that it had 1 twice, but negative the first time and positive the second time. So I figured it was a loop of length 3 with negation of the "changes" in alternation -- therefore (7-6)x8=8-->7(x)8=8. An expression for this would not be as easy to create. I'd prefer a piecewise function like this: a(x)b={a-(1^(a mod 2))xb for a mod 3=0, a-6(1^(a mod 2))xb for a mod 3=1, axb for a mod 3=2}. I think 224 is a way better answer, though!

[@user-rv2xw5yb1s]

exactly what I thought

[@hervelens]

No, this is a good answer as well ! Any working pattern is good, so, good job!

[@randomgamer-te8op]

honestly, this is a way better answer for me than the purposed and "suppossedly correct" one, love it!

[@_catzee]

I'm glad you guys liked my answer and thought the same way! The reason 224 makes more sense in my mind is that to represent a(x)b doesn't require a piecewise function or even a modulo function. a(x)b=ab^2/gcd(ab^2,6) is much more elegant to me than a(x)b={a-(1^(a mod 2))xb for a mod 3=0, a-6(1^(a mod 2))xb for a mod 3=1, axb for a mod 3=2}.

[@randomgamer-te8op]

@@_catzee i have no idea what any of that means so im gonna stay with the new one kekw

[@davidbelk46]

That's definitely an interview I would have failed😑

[@jmyhe]

Directly following from your solution, and the GCD-LCM formula, another interpretation is: lcm(ab², 6)/6

[@thatsmykulture7266]

If i get asked this question in an interview im definitely gonna start taking hostages n become a cannibal

[@dashingrapscallion]

Playing around with the numbers I came up with ((-1)^a/4 + .25)(104-a) + ((-1)^a/2 - .5)(25-11a) That will do it as well 😊 With an output of 52 for 7x8 I pulled out the first and third equation and made a line that connects those two and also pulled out the second and fourth equation and made a line connecting those two. Then I just controlled which line I accessed by multiplying each by -1 to a power (slightly edited by simple arithmetic to get 0 or 1 instead of -1 or 1) and summing them together. My -1 to a power kind of acts like an on/off switch to control which line I want depending on whether the a value is even or odd

[@comteharbour]

First solution: All results are multiple of the 2nd number. However, it cannot be a combination of additions and multiplications with the two numbers, otherwise the results would be monotonous growing. So: let's assume there is a rule that affects the 1st number (since the second divided the result). What should we have ? 2*4=8, hence 3->2 (-1) 10*5=50, hence 4->10 (+6) 5*6=30, hence 5->5 (0) 7*7=49, hence 6->7 (+1) For symmetry reasons, I assume that the next one would be (-6), hence 7-6=1 and 7×8=1*8=8 I am not convinced. Second solution. The results follow an up-down-up pattern. The simplest function that can do that is 3rd degree polynomial. Besides, even if the function looks like having two variables, the pattern can be described with just one: (n)×(n+1)=f(n). We also need 4 points to describe a 3rd degree polynomial, and we just have that: (3;8), (4;50), (5;30), (6;49). Let's define f(x)=ax^3+bx^2+cx+d Let's solve the system f(3)=8; f(4)=50; f(5)=30; f(6)=49 We get a=101/6; b=-233; c=6301/6; d=-1500. So f(x)=101/6*x^3-233*x^2+6301/6*x-1500 So f(7)=...=208 Therefore 7×8=f(7)=208 It feels like an overcomplicate approach, but it's logical. Third solution: I have some debatable solutions. I have some more ideas. It's clear that I lack information like context and meaning of these symbols to decide which ideas are worth investigating. Therefore I need to investigate the context. For example: who the hell wrote those 4 lines of code without commenting nor testing ? Do I get the job?

[@rajveersingh2056]

One pattern, if × is not multiplication, then why = would be equal... It fits this pattern, make 3%4 != 8 So 7 % 8 != 10 So the answer is 10.

[@bocagelandscape]

I also thought about the x and equal thing. But then we can give more than one interpretation to the symbol x, while I can't really come up with another interpretation of two parallel lines.

[@CoverBydAn]

In a similar riddle, i saw someone say: 56. The fact that everyone else did it wrong doesnt mean i hv to also be wrong. Life changing.

[@stevens326]

Perhaps the pattern isn't 2 or 6, but rather every integer divisor until the next division is no longer an integer. So instead of 2 or 6, it's [1, 2,] or [1, 2, 3], and potentially [1,2,3,4]. Same answer, but the 2/6 problem is explained.

[@plinkiplonk]

That would have given you a divisor of 5 for the second line, not a 2, no?

[@Bovineprogrammer]

@@plinkiplonk No, the idea is you divide by each integer in turn until it fails. For the second line, 4 (x) 5 is calculated: 4*(5^2) = 100. Can you divide 100 by 1? Yes -> 100. Can you divide 100 by 2? Yes -> 50. Can you divide 50 by 3? No, so stop and the final answer is 50. The issue with this logic is actually the first line - 3 (x) 4 becomes 3*(4^2) = 48. Can you divide 48 by 1? Yes -> 48. Can you divide 48 by 2? Yes -> 24. Can you divide 24 by 3? Yes -> 8. Can you divide 8 by 4? Yes -> 2. Can you divide 2 by 5? No, so stop and the final answer is 2. However, 3 (x) 4 is given as 8, so this cannot be the correct process. The first question rejects the possibility that you are attempting each integer in turn until one fails; however, it doesn't reject the possibility that you're only dividing by prime numbers - instead, the third question rejects that one by being divisible by 5 even after having been divided by both 2 and 3. But I do like the thinking - if it held, it would be seemingly less arbitrary than "gcd of number and 6".

[@BapiKAR]

I tried to inspect the prime factorisation of each sequence on the LHS & the corresponding pattern in the prime exponents. If you see 3*4 and 7*8 has an interesting pattern match in the exponents. That leads 7*8 I.e. [2,7]^[3,1] to [2,7]^[5,1] I.e. 2^5*7^1 = 224. Hope I could explain it?

[@doctorfun8851]

Following simple/generic method gives multiple solutions (potentially infinite). a. Ignore the second variable: We are given four values for the application of a binary operation 'op' of the form 'x op y'. Since, y = x + 1, we will ignore y and use a function 'f(x)' of single variable 'x'. b. Create a function for f(x): We are given four values of f(x), f(3) = 8, f(4) = 50, f(5) = 30 and f(6) = 49. We can create a form for f(x) and set up a system of equations with four unknowns. Solving the four unknowns gives the value for f(7). Suppose f(x) = a.A(x) + b.B(x) + c.C(x) + d.D(x). Following are two solutions. Solution 1: f(x) is polynomial. A(x) = 1, B(x) = x, C(x) = x^2 and D(x) = x^3. f(x) = a + b.x + c.x^2 + d.x^3 solving the system of equations gives a = -1500, b = 6301/6, c = -233, d = 202/12 f(x) = -1500 + 6301.x -233.x^2 + 202/12.x^3 and f(7) = 208. Solution 2: f(x) is exponential. A(x) = 1^x, B(x) = 2^x, C(x) = 3^x and D(x) = 4^x. f(x) = a.1^x + b.2^x + c.3^x + d.4*x solving the system of equation gives a = -147.8333333, b = 41.4375, c = -8.796296296, d = 0.966145833 f(x) = -147.8333333 + 41.4375.2^x - 8.796296296.3^x + 0.966145833.4^x and f(7) = 1748. The more forms of f(x) we can create, the more solutions we get.

[@minhcongnguyen5917]

Another way to write the formula is a*b=lcm(ab^2,6)/6

[@lukeellis3167]

Recognizing that 7^2 is 49, I came up with a x b = max(any duplicate factors of a,1) times (the lowest prime factor of b raised to the lowest prime factor of a) - (max(the product of any remaining unique prime factors of b,1) - 1), so: 3x4 = 1x2^3-(1-1) 4x5 = 2*5^2-(1-1) 5x6 = 1*2^5-(3-1) 6x7 = 1*7^2-(1-1) 7x8 = 1*2^7-(1-1) = 128

[@williamr5618]

the way I see, it, without looking at the numbers, I'd think that the results follow an odd-even pattern. so there's a pattern for the odd terms (8, 30, ...) and for even terms (50, 49, ...) Looking at just the odd terms, and seeing the relationship with the numbers: f(3, 4) = 8 f(5, 6) = 30 f(7, 8) = ? I attempted to deconstruct the pattern: 3(4) = 12 8 - 12 = -4 5(6) = 30 30 - 30 = 0 Taking the difference between the result to (ab) increasing by 4 each term, I argue that 7(8) = 56 56 - x = 4 x = 56 + 4 = 60 the answer to 7 X 8 is 60

[@selfishvirtue28]

Lol

[@paulmayer8654]

Without watching the video yet, the answer I came to was 46. Here’s how…the sequence is xy-y, xy+y, xy, then reversed xy+y, xy-y 7x8-8=46. Now let’s see what the video says 😂

[@vicpinto1970]

I was looking at this in terms of something other than a base-10 numbering system. The numbers are in quotes because this is a fictional number system. So "3"x"4"="8" equates to "4"="8"/"3" - this is the value of "4". Now feed this into the next equation. Equation 2 equates to "5"="50"/("8"/"3") - this is the value of "5". Now feed that into equation 3 and so on. The last equation is simple in that you already know what "8" is - it's "3"x"4" and you've calculated "7" from the previous calculations. This is another possibility in an infinite number of possibilities that work.

[@maximilianweber2150]

I also found 224 as a solution but did not construct a function to generate the given results but rather consider the serial character of the problem. First, I calculated the product axb and the relative deviation to the given results, e.g. 3x4 = 12*2/3. This gives you for the relative factors 2/3, 5/2, 1, 7/6 as a new sequence. Writing it in terms of 1/6 I found 4/6, 15/6, 6/6, 7/6. Since 15/6 cannot be replaced with 5/6 as it will not give an integer result I accepted this as an explanaition (a very unpleasing one to be honest). This in turn gives also 224 for 7x8. Which has to be mentioned: since the numbers on the left increase in steps of 1, the function just behaves like a sequence and my solution could be considered identical to the solution given in the video. What we would need is a 6th equation breaking the pattern, like 3x5. Edit: what i forgot to mention: my explanation of the 15/6 was simply take multiples of 5 until the complete product is an integer. For 7x8 this will give 7*8*24/6 as neither 7*8*8/6 nor 7*8*16/6 give integers.

[@archimidis]

I got 208 which is relatively close to 224 by using a different method: First, since the left hand side of the "equations" grows by 1, let's ignore it and focus only on the sequence 8,50,30,49,? Now let's find a 3rd degree polynomial such that f(0)=8, f(1)=50, f(2)=30 and f(3)=49. After solving the resulting 4x4 system of equations we get f(n)=(101n^3-489n^2+640n+48)/6 which gives f(4)=208 as another possible answer. Note that this method also involves division by 6. Also note, it can be proven easily that f(n) is always an integer and thus we can use it to find any number from the sequence that we wish. Unfortunately, f(5) diverges a lot from what we would get for 8x9 using the formula in the video.

[@ivanhorbenko7529]

I found a very weird pattern. Let first number to be `a` and the second to be `b`. The function producing the desired result is very long looks like this: f(a, b) = a + (((b div 6) - 1) * 5 + (b mod 6) + (b mod 6) div 5 * 6) * b And so for the pair of (7, 8) the result is 72.

[@markmurto]

First, I can take any numbers, put them through complex functions randomly, and then ask you to solve something that has only one hidden key.... that I threw in the river. How does making a puzzle like this even count or matter unless it's the Anigma Machine? Even then they used Hile Hitler to solve the daily patterns. This one had and has no purpose.

[@huzefa6421]

while u did ab i saw a pattern 12 + 8 = 20 20 + 10 = 30 30 + 12 = 42 42 + 14 = 56 Now replacing the entire problems starting multiplicand of 3,4,5,6 and 7 we get a new pattern 56 × 4 = *224* ( 56 + 16 ) × 5 ( 72 + 18 ) × 6 and so on

[@s.g.b.808]

Just type „false statement“ behind the equations and this should be a „true statement“ 🤷🏽‍♂️

[@luismartin-roldancervantes7833]

The way I saw it, 4x5 is a red herring. Assuming this is a sequence, removing this element from it you have that the answers can be worked out by adding (i-2) to the first element before performing the multiplication, with i = position in the sequence (starting at 1). Thus: 3 x 4 becomes (3 + (1 - 2)) x 4 = (3 - 1) x 4 = 2 x 4 = 8 5 x 6 becomes (5 + (2 - 2 )) x 6 = (5 + 0) x 6 = 5 x 6 = 30 6 x 7 becomes (6 + (3 - 2 )) x 7 = (6 + 1) x 7 = 7 x 7 = 49 7 x 8 becomes (7 + (4 - 2)) x 8 = (7 + 2) x 8 = 9 x 8 = 72 This was the most satisfying answer I could come up with in 2 minutes (interview simulation lol). Sometimes you gotta get rid of outliers 🙃

[@slendermenan]

Yeah, but you forgot about 4x5=50

[@luismartin-roldancervantes7833]

@@slendermenan i purposefully leave it out. That's the whole point ^^'

[@luismartin-roldancervantes7833]

@@slendermenan I made it a point, intentionally, to not include 4x5=50

[@hyperboloidofonesheet1036]

An answer is 208, which can be determined using finite differences. One gets a cubic polynomial equation for n X (n+1). It doesn't answer what the X operator does, just what the result is with two consecutive integers.

[@gamersboyz5787]

But how can you solve the last 7*8 I am unable to see any pattern in that, my answer is coming 245 .

[@hyperboloidofonesheet1036]

@@gamersboyz5787 Two points makes a line, three points a parabola (quadratic curve), four points a cubic curve.

[@JackPullen-Paradox]

A simple function that exactly fits the known data is probably best. That is not to say that a puzzle author might not have used some random difference polynomial to generate the numbers. The author could have said, Well today a X b = f(a, a + 1), = g(a) = 5a*2 - 3a + 4. But that seems less likely than the author saying Well today a X b = g(a) - a(a + 1)^2 (itself a polynomial); less random.

[@JackPullen-Paradox]

There are a number of finite difference functions that are possible with this data, e.g., the central difference would give you 54.25. For divided differences, the solution would be approximately 208.

[@chrishelbling3879]

I will be sure to use this problem next time I hire a gardner.

[@conrad5342]

Using the GCD could also create a devisor of 3, but there is no such test case to neither support nor contradict its application.

[@risingalpha7232]

Think again

[@OldHeadTrivia]

I would’ve said 23, if you start carrying the inconsistencies down the line you start with +4 then you have -30, 0 and -7 which ends up being -33. Meaning the left side would be in the negative 33. Thus the right side would need to be 33 less than the completed equation on the left. Which is 23. Completely strange logic I know, but it just shows how the brain can work when we’re trying to make something that doesn’t make sense, make sense haha.

[@gary.h.turner]

Sorry, why does it "end up being -33"? That doesn't make any sense to me! Edit: Oh, you mean that the sum of +4, -30, 0 and -7 is -33. I'm not sure if that's relevant!

[@Lovuschka]

Before watching: The answer is 64. You have two streams of numbers, one counting down from 50, the other being 2x4, 5x6, 8x8, etc. (the actual multipliers increase by 3 on one side and 2 on the other). The following things to display would be 8x9=48, 9x10=110, 10x11=47, 11x12=168, 11x12=46, etc.

[@rodrigomarinho1807]

I used the formulas for cords in a circle. When two are perpendicular the products of the segments are equal. Let x the "excess" on the left side and y the "excess.on the right side. So x + y + 3 = 2r And also x(y + 3) = 1 y(x + 3) = 1/4 Solve this system and you get x = (sqrt (185) - 11)/8 y = (sqrt (185) - 13)/8 So x + y + 3 = sqrt (185)/4 R = sqrt (185)/8

[@pauldowney9292]

Presh, Sometimes you have to raise the bs flag. A smart person has enough confidence in themselves to not just go along with a bs answer. You can always do a nonsense fit to data. The person that wrote this perhaps just wanted an unanswerable question in the test. I was asked a trick seemingly unanswerable question on a job interview. A degree in physics and being familar with many coordinate systems helped me answer the question and describe the question as a coordinate singularity point. I did not get the job.... maybe I still haven't learned my lesson. Presh, thanks for your great work making math fun.... Paul.

[@fredashay]

Before watching your video, I would treat the numbers "3" "4" "5" etc as symbols instead of number like in that riddle where an pizza slice + 2 cats = something and 1 cat + 2 apples = something. So for this, I assume that "5" is actually 10, and "4" is 5, and "6" is 3, and so on...

[@fanb0y777]

All this so I can ask “Would you like to get fries with that?”.

[@missy1806]

Just wondering if anyone remembers Presh talking about an online math program that's able to give answers and shows the way it managed to solve it? I don't remember what it's called but it was for any type of math equations, not just basic ones...

[@psychedforlife7176]

What position would someone applying for where they would encounter such an interview question?

[@carultch]

And more importantly, what the heck does it have to do with your qualifications for the job?

[@paulmayer8654]

The question is designed to see how people think, so basically any job that would require out of the box thinking to solve difficult situations.

[@user-vf2bd8yl3m]

I think it can be another pattern. For example, 3×4=3×2^2. And 5×6=5×[2×3]. So we can change like this. 3×2^2=8 2^2×5=50 5×[2×3]=30 [2×3]×7=49 Of course, real answer is 12,20,30,42. But we can figure out the right number is multiplied by real answer. 1. 8=12×(2/3) 2. 50=20×(5/2) 3. 30=30×(1=[5/5={(2+3)/5)}]) 4. 49=42×(7/6) The another pattern i found is about number's 'prime divisor number'. I call that PD. We can group of left number's PD. it means if divisor*mod(any number except itself or 1)=0, it is not PD. So 6=PD(2,3), 4=PD(2). Then, problem's multiply icon means= A×B=A*Sum[B's PD]*B/Multiply[A's PD]. Then 1. 3×4=3/3*4*2=8 2. 4×5=4/2×5×5=50 3. 5×6=5/5*6*(2+3)=30 4. 6×7=6/6*7*7=49 Then, the 5th answer is 7×8=7/7*8*2=16 The another Solution is 16. That's the answer!

[@patricklydon8329]

Multiply ab by a factor of b/6. If the answer isnt an integer, multiply by (b + 10)/6. Thus, the solution is 7x8 x 18/6 = 168.

[@MakaylaTeggor]

There's only one situation (4x5) where you divide ab^2 by 2 instead of 6, and there are various other simple rules for why 4x5 is the one exception. For example, '4' and '5' each are drawn with a horizontal line segment. If there is a horizontal line segment in each of the numbers, then the rule is: (1) superpose all the horizontal line segments of all of the digits, (2) rotate by 90 degrees, (3) interpret the result as a Roman numeral, (4) use that value as a divisor. If there isn't a horizontal line segment in each of the numbers, the divisor is 6. Here, for 4x5, you start with one horizontal line segment above the other, rotate by 90 degrees to get the "II" letters, interpret "II" as 2, and thus the divisor is 2. With 7x8, there is no horizontal line segment in the '8' and thus the divisor is 6 and the final answer is 74 2/3.

[@ClickBeetleTV]

It's odd how many of the people in these comments get bogged down by symbology, angrily, even. Mental flexibility and the ability to interpolate meaning and intent in novel uses of the previously familiar are not negatives, kids

[@tarajoyce3598]

I chose 7. SUPER SIMPLE Only considered the answers after no quick pattern. The 30 is correct math for the given equation. Started there. Followed the pattern of bottom answer being one less than corresponding top answer.

[@imqqmi]

Not brilliant but my guess was how to get to the correct answer of the equation by adding/subtracting from the first number (3-1)x4 = 8, (4+6)x5 = 50 etc. Then at 6x7=49, you add one, which is the first equation (-1) with the sign flipped, so the next would be -6 ie (7-6) x 8) = 1.

[@MrWarlls]

Wow, I think I would never have found the solution.

[@AThousandYoung]

Answer is 1/5. The student who turned in this paper got four of them wrong.

[@paulangelo1974]

I read it as a riddle not a math problem. 5x6 does equal 30 and it is the middle equation, thus it is the base line. (3x4=8) - (4x5=50) = -42, which is (6x7), below the base line. (4x5=50) - (5x6=30) = 20 which is 4x5, above the base line. Finally (5x6=30) - (6x7=49) = -19, below the base line. So my solution is 7x8=19. To check, (6x7=49) - (7x8=19) = 30 which is 5x6, the base line.

[@TomKaren94]

As an accountant, my answer would be "What do you WANT it to be?"

[@anbuchelvan4382]

I got 24 in the first 3 x 4 = 8, they did 3 x 3(4-1) - 1 Next 4 x 5 = 50, they did 4 x 6(5+1) + 1 and multiplied the whole value x 2 Next is the mid value so it was right 6 x 7 = 49, they di 6 x 8 (7+1) +1 so 7 x 8 = 7 x 7 (8-1) - 1 and whole divided by 2, we get 48/2 = 24 I got 24, the interview answer is 224 ..... hmmmm interesting lol

[@selfishvirtue28]

Lol

[@mehrozmustafa9513]

The X inside a circle symbol is also used to represent the XNOR gate, so it’s a bit misleading then again its just a fun maths riddle so any thing can have its own meaning.

[@KZgun4hire]

Simple pattern substitution of : if expressed in this manner (value and correction) X value = answer. Then 3 x 4 = 8 is expressed as (3 - 1) X 4 = 8, and ... (4 + 6) X 5 = 50, (5 + 0) X 6 = 30, (6 + 1) X 7 = 49, (7 - 6) X 8 = 8. In this solution we are following a pattern of corrections to provide the expected answer. The correction presented here form a pattern of simple constants ignoring the sign of 1, 6, 0, 1, 6. And with the sign we find the pattern -, +, neither, +, -. The two patterns combined form -1, +6, 0, +1, -6.

[@paulm8791]

So we are saying that 7*8 doesn’t = 56 now. If I put 56 and they say it is wrong, I wouldn’t want to work there.

[@lawrencejelsma8118]

Who said 7 x 8 = 56 was not correct. I thought everything above showed a multiple choice example where one has to be correct and the others wrong. So 5 x 6 = 30 was the only correct multiplication result and the other three wrong; meaning, a hanging equation of ? equation result is implied by the previous multiple choice one correct answer I thought was an example! ☺️😂

[@denvercheddie]

It could be that if either of the 2 numbers is divisible by 3, then you use 6. Otherwise 2???

[@Arcessitor]

By rearranging the symbols: 4 x 4 x 5 = 30 + 50 (the + here is just a rearrangement of where 50 is) 7 x 7 = 49 6 x 8 = 6 x 8 3 x 5 == 15 Answer is 15. Empathetically so.

[@chrisg3030]

My answer is 23. Add up all the correct products, 12 + 20 + 30 + 42 + 56 = 160. Now add up the products actually given, 8 + 50 + 30 + 49 = 137. The missing product for 7 x 8 must be 160 - 137 = 23. I'd be great plugging holes in their accounts.

[@roger7341]

Wow, am I fortunate that I didn't interview for a job with that company. In my last job interview they asked if I could develop a computer model of a complex machine they were having problems with. I said yes and proceeded to show how them how I would do that and the results they should expect. I got the job.

[@Mngalahad]

But how do they really know if youre good for the job if they dont ask you how many jellybeans fit in an airplane sized golfball?

[@kirkjohnson6638]

The interviewee had the advantage of knowing for what type of job they were applying. For all we know they could have been applying for a job at a restaurant and the a values were quantities ordered, the b values were item numbers on the menu, and the results were the total cost for that number of menu items.

[@jennystrandqvist1568]

If 3x4 gives 2/3 of the correct answer and 4x5 gives 5/2 of the correct answer then I hoped it would be something like axb = (b/2)/a for a pattern, but then there was 5x6 giving 1/1 of the correct answer, and 6x7 giving 7/6 of the correct answer, so I had probably guessed 7x8 would give 8/7 of the correct answer =~74.5 ... (7x8 = 56, 56x(8/7) = 74.48) ... 208 with "Newton's forward interpolation" or 224 as shown in the video is 371% and 400% of the correct answer, so no way getting there thinking of what it should have been.

[@manusarda]

I hate whenever viewers fails to answer some questions they don't appreciate the level of question but rather post comments saying how the question is wrong.

[@samarthmehta8732]

Such puzzles are the reason why we will never have world peace.