Puzzles

MICROSOFT     Interview Puzzle:

CLOCK HANDS:

1.Question: How many times a day do the minute and hour hands of a clock overlap?

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Answer: Did you think the answer was 24 times? Well if you did, it’s time you think again. Let’s do some math.

In T hours, the minute hand completes T laps. In the same amount of time, the hour hand completes T/12 laps.

The first time the minute and hour hands overlap, the minute hand would have completed 1 lap more than the hour hand. So we have T = T/12 + 1. This implies that the first overlap happens after T = 12/11 hours (~1:05 am). Similarly, the second time they overlap, the minute hand would have completed two more laps than the hour hand. So for N overlaps, we have T = T/12 + N.

Since we have 24 hours in a day, we can solve the above equation for N

24 = 24/12 + N

24 = 2 + N

N = 22

Thus, the hands of a clock overlap 22 times a day. Thus the hands of the clock overlap at 12:00, ~1:05, ~2:10, ~3:15, ~4:20, ~5:25, ~6:30, ~7:35, ~8:40, ~9:45, ~10:50. Note that there is no ~11:55. This becomes 12:00.

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INFOSYS 

TWO CANDLES  puzzle

1. You are given two candles of equal size, which can burn 1 hour each. You have to measure 90 minutes with these candles. (There is no scale or clock). Also u r given a lighter.

       

Ans: First light up the two ends of the 1st candle. When it will burn out light up one end of the second candle.   (30+60=90)
    

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PYRAMID PUZZLE:

2.How it is possible to place four points that are equidistance from each other?

  

Ans: Only 3 points can be equidistant from each other. But if u place points in the shape of a pyramid 

then its possible.

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GOOGLE INTERVIEW PUZZLE

You have a set of 3 light switches outside a closed door. One of them controls the light inside the room. With the door closed from outside the room, you can turn the light switches on or off as many times as you would like.

You can go into the room - one time only - to see the light. You cannot see the whether the light is on or off from outside the room, nor can you change the light switches while inside the room.

No one else is in the room to help you. The room has no windows.

Based on the information above, how would you determine which of the three light switches controls the light inside the room?

ANS:     first switch on 1st one and wait 5 min and off . and now switch on 2nd one and goto room and see
there is one bulb which is glowing that is 2nd switch bulb  and now touch all bulbs with your hand  one bulb heated  that belongs to 1st switch and remaining bulb belongs to third switch.
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