Test includes questions on machine learning models, brain teasers, probability questions.

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different. How do you measure 45 minutes?

(Let me know if you want the answer to this)

EDIT: It's around 15 questions. Also includes some standard IQ questions.

 

it says that it takes exactly one hour to burn, correct? Would tracking when only 25% of the string is remaining not tell you that 45 minutes has gone by? Inbox me the answer if you could as I am pretty certain that I am missing the question completely lol.

 

I'll PM you but commenting to clarify for other readers. The rate of the burn is unknown so that answer wouldn't suffice.

EDIT: Can't PM you as I met my limit.

 
Best Response

Light both ends of rope A and one end of rope B. After 30 minutes, rope A will be completely burned up and there will be 30 minutes of rope B left. Light the other end of rope B; it will burn up in 15 minutes.

 

Here's another common question asked in interviews:

You have a scale and 8 pills. One pill is poisonous and weighs slightly more than the other 7 pills. You can only use the scale twice. How do you find which pill is poisonous?

 

assuming each string burns at a random and FIXED rate (each half of the string each burns in 30 minutes, seems like the question permits that): pick a string, fold it in half. fold it in half again. cut off one end of the string at the fold. the remaining string is 3/4ths of the length of the original string. light it. it will burn for 3/4 of an hour = 45 min.

 

To measure 45 minutes with these two ropes, you should first light both ends of one rope. At the same time, only light one end of the second rope. When the first rope is completely burned up, 30 minutes will have elapsed. At this point, you should then light the other end of the second rope. Because there are 30 minutes left of burn time on this rope, lighting the other end will cut that time in half, leaving you with 15 minutes of burn. Overall, you will have burned through both ropes in 45 minutes.

 

Ok, I think all the below people might have taken a different test. The test I took was very advanced level statistics/probability/pure maths/CS questions, like advanced undergraduate level (think, what is the poisson distribution in this scenario etc.). If you have experience of brain teasers then the rope burning one really pales in comparison. With that being said, if you want a good site on brain teasers, this might be helpful: http://puzzles.nigelcoldwell.co.uk

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