Classic math puzzles for job interviews
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Classic math puzzles for job interviews
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Re: Classic math puzzles for job interviews
#2Ok, I fail and don't get the job, I get it... but where are the answers!
Re: Classic math puzzles for job interviews
#3on the mouse one, could you not mix wines?
100 bottles, divide into 2 groups, feed mouse...
Separate poisoned bottles into 2 groups feed mouse..
basically 100,50,25,12,6,3,1 ... 6 mice needed.
Re: Classic math puzzles for job interviews
#4These problems are a lot of fun and in most cases there are interesting general lessons in their solutions, but the way the interview system seems to work is that every year there's a new book or sheet of puzzles that everyone memorizes and then pretends to have never seen before when asked during an interview.
Re: Classic math puzzles for job interviews
#5on the mouse one, could you not mix wines? 100 bottles, divide into 2 groups, feed mouse... Separate poisoned bottles into 2 groups feed mouse.. basically 100,50,25,12,6,3,1 ... 6 mice needed.
There is only 1 day. Wouldn't you just separate the bottles evenly across all the mice?
Re: Classic math puzzles for job interviews
#6These problems are a lot of fun and in most cases there are interesting general lessons in their solutions, but the way the interview system seems to work is that every year there's a new book or sheet of puzzles that everyone memorizes and then pretends to have never seen before when asked during an interview.
Yeah, these puzzles are too unique and are in many cases well known problems/paradoxes that candidates are likely to know. Interviewers might be better served by asking a generic, LSAT-style logic game or a somewhat simple but time consuming math problem (maybe polynomial factorization).
Re: Classic math puzzles for job interviews
#7#5 is impossible. Martin Gardner has a nice proof of this: observe that each domino must cover a black and a white square, no matter how you orient it. When you remove two opposite squares, you remove two squares of the same colour. Imagine you have put 30 of the dominoes on the board, then two squares remain uncovered. These squares must be the same colour (by the above rules), so there is no way the last domino can cover them both.
Re: Classic math puzzles for job interviews
#8on the mouse one, could you not mix wines? 100 bottles, divide into 2 groups, feed mouse... Separate poisoned bottles into 2 groups feed mouse.. basically 100,50,25,12,6,3,1 ... 6 mice needed.
There is only 1 day. Wouldn't you just separate the bottles evenly across all the mice?
That way you could serve 900 bottles. Can you serve more?
Hint: Look at the number of possible outcomes. In this case, each of the 10 mice can either live or die. That gives us 2^10 = 1024 possible outcomes. We can only encounter 1000 possible initial configurations of bottles. Is there a way to set it up so that each of the 1000 possible outcomes maps to an initial configuration?
Re: Classic math puzzles for job interviews
#9Wow, I am surprised #13 is listed as a 1-star problem.
I was told a story about this problem by a professor while in class. Supposedly, Edgser Djisktra couldn't sleep one night due to jet lag. He was currently going through a phase in which was exercising the power of thought, practicing thought-exercises such as these without a pencil and paper. While in bed that night, awake due to jet lag, he solved this problem. The professor told us that none of us were smart enough to solve this problem. Hardly seems worthy of one star. :)
Re: Classic math puzzles for job interviews
#10Earlier quoted context omitted.
There is only 1 day. Wouldn't you just separate the bottles evenly across all the mice?
That way you could serve 900 bottles. Can you serve more? Hint: Look at the number of possible outcomes. In this case, each of the 10 mice can either live or die. That gives us 2^10 = 1024 possible outcomes. We can only encounter 1000 possible initial configurations of bottles. Is there a way to set it up so that each of the 1000 possible outcomes maps to an initial configuration?
I figured it out by thinking what would happen if you only had 1 mouse (500 bottles can make it to the party), then looking at the problem again with 2 mice (there's a way to prove that 750 bottles are poison-free using only 2 mice), etc. all the way up to 10 mice.