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Answers to the most common puzzles in Interviews PART-3

Here are the answers for my last post of Common puzzles in Interviews.


1. Planes will not collide if they all move in same direction (Clockwise or AntiClockwise). So each plane has 2 choice , either clockwise or anticlockwise. So for all the planes we will have 2^5  possibilities.

Below are the possibilities for all five planes where C denotes Clockwise and A denotes AntiClockwise

CCCCA
CCCAA
CCAAA
:
:
:
:
CCCCC
:
:
:
AAAAA
:
:
AAAAC

So in all we have 32 possibilities and out of those 32 only 2 possible combination (AAAAA & CCCCC) will not result into collision.

So probability of planes not getting collide is 2/32 = 1/16.

2. The next number in series is 23.

2 11 -> 2+(1+1) = 4
4 15 -> 4+(1+5) = 10
10 13 -> 10+(1+3) = 14
14 18 -> 14+(1+8) = 23

3. So in one day the net time increased is 1/2 - 1/3 = 0.17 minutes .
Clock will become 5 minutes faster in
0.17 * days = 5
days = 5/0.17 = 29.4 days ~ 30 days.
So the date will be 30th of May.

4 . The next number in series is 256
1/5 -> 5^1 = 5
3/6 -> 3^6 = 216

Similarly, 4^4 = 256

5. Singapore is 10 hours behind brazil and dubai is 6 hours behind brazil. So Dubai is 4 hours ahead of Singapore.

So if you travelled for 6 hours , you will reach dubai at 15:00 PM dubai time.

After that you travel for 15 hours 15 minutes to Brazil , so you will reach brazil at 12:15 PM next day brazil time.

Please let me know in comments if you have different answers or approach.

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