100 Door Puzzle Solution

To understand the solution let's take an example. let us take the door number 15. so 15 will divisors as 1&15 and 3&5. So after this pass it will come back to it's original position because 1 will open,3 will close,5 will open and 15 will close.So the door will remain in it's original state. But what about the door 25. it has 1&25 and 5&5 as it's divisors. But since 5 will occur only once so after all the passes 25 will be open. So this means that all those which are perfect squares will be open and rest will be closed.

100 Doors Puzzle

You have 100 doors in a row that are initially closed. You make 100 passes by the door and change it's status i.e (you make the closed door open and the open door closed). After the first pass
 you visit every 2nd door(i.2,4,6,8...) and in the next pass you visit every 3rd door and so on.
After all the pass which doors are closed and which are open.

Ants on a Triangle Puzzle Solution

Well let's see all the possibilities of this puzzle. there are total 8 possibilities for this puzzle in which the ants can move. Let us assume a triangle ABC. So the 8 combinations will be

1.  A->B, B->C, C->A
2.  A->B, B->A, C->A
3.  A->B, B->A, C->B
4.  A->B, B->C, C->B
5.  A->C, B->C, C->A
6.  A->C, B->A, C->A
7.  A->C, B->A, C->B
8.  A->C, B->C, C->B

So in these 8 possibilities there will be two non colliding movements
1 and 6.

So the probability will be 2/8 = 0.25.

Ants on a Triangle Puzzle

This is one of the good probability puzzle asked in interview questions. There are 3 ants on each corner of a triangle. At a given point of time they all start together for a different corner at random.What is the probability that they will not collide.

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Bridge Crossing Puzzle I Solution

Well this is possible. the only trick is in realizing that you want to get the two slowest people across together, because otherwise you are wasting too much time. but then once you get them across, how do you not make one of them walk back with the flashlight? well, you just have one of the fast people already there waiting to sprint the flashlight back across.
1. A & B crosses with flash light: 2 mins total time: 2 mins.
2. A comes back with flash light: 1 minute Total = 3 mins
3. C & D crosses with flash light: 10 mins Total=13 mins
4. B comes back with flash light: 2 mins Total=15 mins
5. A & B cross = 2 mins Total=17 mins

Bridge Crossing Puzzle I

This is a classic puzzle asked in most of the interview questions. Well there are four persons A,B,C and D. All the four persons takes different times to cross the bridge.
person A :1 minute
person B :2 minutes
person C :5 minutes 
person D :10 minutes
There is only one Torch available and it is required in crossing the bridge.Two persons can cross the bridge at the same time but will take the time the of the slower one.For Example : if A and C wants to cross the bridge first they will take 5 minutes. All the four persons can come to the other side in 17 minutes. Can you Explain how?

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1000 Bottle Puzzle Solution

The solution is simple since 2^10=1024>1000 is the answer for this puzzle.Confused let me explain
number the bottles 1 to 1000, and write the number in binary format.

bottle 1    = 0000000001
bottle 250  = 0011111010
bottle 1000 = 1111101000

now take your prisoner’s 1 through 10 and let prisoner 1 take a sip from every bottle that has a 1 in its least significant bit. let prisoner 10 take a sip from every bottle with a 1 in its most significant bit. etc.

prisoner    10 9 8 7 6 5 4 3 2 1
bottle 15    0 0 0 0 0 0 0 1 1 1

for instance, bottle #15 would be sipped by 3,2 and 1. that way if bottle #15 was the poisoned one, only those prisoners would die.

1000 Bottles Puzzle

A king has 1000 bottles of wine of same type.His rival king decides to kill him and send his secret killer to poison one of this wine bottle.The killer poison one of his bottle but was caught by the guards.The King came to know about this and he decides to check which bottle is poisonous. The king is very clever so he decides to take 10 prisoners from his jail to check which bottle is poisonous or not. Can you explain how it is possible?

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8 Ball Puzzle Solution

There are two solutions for this puzzle. One solution is

Divide the balls into 4-4 each
Weigh them against each other. The side which has the heavy ball will weigh more and remove the other 4.
Now divide them into a pair of 2-2.
Again measure them and take the side which weighs heavier.
Now weigh the two balls against each other and you will find the heavier one.
In total it will take 3 weighing.

Other Solution

Divide the balls into three pairs as 3,3,2.
Now weigh the 3-3 balls pair.
If you find them balanced then just weigh the remaining two you will get the heavy ball.
If the weigh is unbalanced take the 3 ball pair which is weighing heavy.
Now take 2 balls and weigh them.
If they are equal then the other ball is heavy or you will find the heavy ball.
In total it will take 2 weighing.

8 Ball Puzzle

This is the most commonly asked interview puzzle. You are given 8 balls of same colour and size.Only 1 among them is heavy and rest are of same weight. You are given a weight balance. In how many weighing you can check which one is the heavier one among 8 balls?

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Rope Puzzle Solution

Well the solution is simple.First take one of the rope and put it's both the ends on fire.Since it takes 1 hour to completely burn a rope but if you put the fire from both the ends it will take only 0.5 hour to burn it.
As soon as the 1st rope is burnt completely take the second rope and put it on fire. it will take 1 hour to burn completely.
So in total we can measure 1.5 hours using both the ropes.

Rope Puzzle

Well this puzzle is asked in most of the interview questions. You are given two ropes of same width and length.The two ropes will burn completely in 1 hour.
You have to estimate 1.5 hours using the ropes.Please note that the ropes are not of uniform cross section. So it may happen that 60% of rope burns in 0.5 hour and the remaining in 0.5 hour.

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Bucket Puzzle Solution

Well the solution is simple. First fill the 5 L bucket completely and empty the water in the 3L bucket. Now empty the 3L bucket and pour the remaining 2L water left in the 5L bucket in 3L bucket. Now fill the 5 L bucket and pour it in the 3L bucket till it is full. You will have 4L water left in the bucket.

Bucket Puzzle

You have two buckets one with capacity of 5 Liters and the other with a capacity of 3 Liters. You have to measure 4 Liters using the two buckets.How will you do it??

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