# The tricky brain teasers interview

Apart from all the technical questions that a banker can possibly throw at you to test how nerdy you are, they also love to test how smart you really are. It is the key objective of brain teasers interview. In our Decoding Brain Teaser Questions, we will let you know the most common types of brainteasers and guide you through the thinking process to tackle these at ease:

1) What is the first time after 3 PM when the hour and the minute hand of a clock meet? (A common question in J.P Morgan’s interview)

Think about this question in a simple way. There are 2 objects (the minute and the hour hand), they move in the same direction at different speed. The hour hand is ¼ of a full circle away from the minute hand (here we start at 3 o’clock, right). How long after the departure they will meet each other?

The minute hand moves around the clock in 1 minute. So its velocity is 1

The hour hand moves around the clock in 60 minutes. So its velocity is 1/60

Let X be time where minute hand and hour hand meet each other. We have the following equation:

X*1=X*1/60+1/4

-> X= 15/59 ~15.3 minutes

So at ~3:15 the minute hand and the hour hand meet each other

2) Give me the decimal equivalent of 13/16 and of 9/16.

This sounds a bit crazy right? How can you remember these fractions? How is it even possible to do all the calculation in your head?

There is a simple solution:

You should remember that 1/8 is 0.125 and deduce from that, 1/16 is 0.0625.

The fraction 13/16 is only 1/16 away from 12/16 (which is ¾, aka 0.75). You only need to add 0.0625 to 0.75 to get 0.8125

Similarly, 9/16 is only 1/16 away from 8/16 (which is 0.5). You only need to add 0.0625 to 0.5 and get 0.5625

3) A snail is climbing up a 10 foot pole. It climbs up by 3 feet every day. Every night it sleeps. While sleeping, it slides down by 1 foot. When does it reach the top of the pole (This is asked in Barcap’s assessment center)

A naive answer is: the snail will reach the top at the end of the fifth day since it climbs 2 feet net every day!

Actually, the right answer is: In the morning of the fifth day, the snail starts at 8 foot height, and 2/3 of the fifth day, it reaches the top and stops because there is no pole left to climb

wrong

nice, only 3 things to remember for any interview!

Snails, poles, fractions and velocity!

woo

these 3 were easy

Thats not how clocks work.

I think that a much more productive text is not how to solve specific questions, and rather how to train for general brain teasers, usually they fall in some category of recreational mathematics or algebra, which are those categories?

That’s an idiotic solution, brah. I wish some JPM dumbass asked me this. What if you start at 12 noon so that the hour and minute hands are lining up? Your equation becomes X*1=X*1/60+0, so then X=60/59. Every 60/59 hours , or approximately 61 minutes they meet again, according to your solution. So they’ll meet at again at 1:01pm, 2:02pm, 3:03pm…10:10pm, 11:11pm, 12:12am?? But we know they should meet again at 12:00am midnight, in exactly 12 hours. What happened?

Aye, though not as crazy as typing that long post only to be ridiculed.

LOL…I read the OP’s explanation 5 times b/c I just assumed I was missing something. But thank you for confirming I’m not in fact crazy. I’m guessing he is referring to the second hand moving around the clock in 1 minute…

I feel like this was copied and pasted from somewhere else. Who is “we”?

A couple questions I have heard:

An investment bank interviewer asked me to calculate the GDP per capita of Jamaica.

Taco Bell asked me to calculate how many tacos a store would sell in one day.

My dad would always use “how many manhole covers are there between here and New York City?”

I’ve mainly heard of questions where the interviewer doesn’t know the answer either. They just want to see how you attempt to solve it. The ones above are just stupid questions you can solve in 2 seconds.

that seems to be more interesting question than thread starters answer and solution.