#391 - Morgan Stanley Induction Logic Interview

The wisest men of the kingdom are called upon by the king to his court. One of them is to be chose for the advisor rank and thus they shall prove their worth in the test. The king places hat on each of their hats. Each one of them can see other two hats but can't see his own. The hats are either white or black.

For a hint, the king tells them that at least one of them is wearing a black hat. Also the king declares that the test is totally fair for each one of them. Now the first one from them who is able to deduce the color of hat he is wearing will be designated as the advisor. After a few minutes, one of them was able to deduce the color of his own hat. How ?

Morgan Stanley Induction Logic Interview

Suppose that there is just one black hat. In such a scenario, the person wearing it will see the other two hats as white and then as the king had announced, he will be easily able to judge that he is wearing a black hat himself. But the other two men will see a black hat and a white hat and will not be able to judge. Thus this will be an unfair situation, so we can rule it out.

Now suppose that there are two black hats. Then, both the person will see a white hat and a black hat. And they have already realized that there must be two black hats, thus they can easily deduce that they are also wearing a black hat. But the one wearing white hat will see two black hats and thus he will not be able to identify on a sure note. Thus the competition will not be fair.

Thus the only situation where the competition can be fair is when all the hats are black. The first one who recognize the fact will stand up and say black.

#392 - Impossible Mind Teaser

During an experiment, a guy throws a bouncy ball from a 90 feet tall building. The ball has a specific characteristic. Every time it hits the ground, it bounces up half way.

How many bounces do you think the ball will make before it comes to a stop ?

Impossible Mind Teaser

Clearly as per the data given in the question, the ball will always keep on bouncing half way up and thus it will take infinite bounces before the gravity forces it to stop.

#393 - Water Jug Puzzle

There are 4 water jug – A, B, C and D.
One can fill 3 litres in A, 4 litres in B, 5 litres in C and 5 litres in D. Container A and B are given to you empty and C and D are fully filled with water.

What you have to do is fill the water jug A, B, C and D with ascending or descending order.

Water Jug Puzzle

Initially
A – 0, B – 0, c -5, D – 5

Pour C into B
A – 0, B – 4, C – 1, D – 5

Pour C into B
A – 0, B – 4, C – 1, D – 5

Pour half of B into C
A – 0, B – 2, C – 3, D – 5

Pour D into A
A – 3, B – 2, C – 3, D – 2

Pour A into B
A – 1, B – 4, C – 3, D – 2

Pour half of B into D
A – 1, B – 2, C – 3, D – 4

#394 - Inmobi Interview Bottle Puzzle

There are two bottles that consists of different pills each. You must take the two pills at the same time and if you forget, or just take one of them or take two of the same kind, you will die a miserable death. In a hurry, you pour from both the bottles at the same time and three pills fall down in your hand.

Now you can’t throw away the pills as they are quite rare to be found. Also both of the pills look exactly the same and have all the characteristics similar. How will you ensure that you don’t take a wrong pill and die ?

Inmobi Interview Bottle Puzzle

All you have to do is labelling the pills as A and B. Now when you draw out three pills, you will either have 3A or 2A 1B or 1A 2B or 3B. Now if all the pills are from same bottle you can simply take another from the other bottle. If some other combination comes out, you can manage by filling in from the required bottles.

#395 - Hard Logic Amazon Interview Puzzle

Two friends were stuck in a cottage. They had nothing to do and thus they started playing cards. Suddenly the power went off and Friend 1 inverted the position of 15 cards in the normal deck of 52 cards and shuffled it. Now he asked Friend 2 to divide the cards into two piles (need not be equal) with equal number of cards facing up. The room was quite dark and Friend 2 could not see the cards. He thinks for a while and then divides the cards in two piles.

On checking, the count of cards facing up is same in both the piles. How could Friend 2 have done it ?

Hard Logic Amazon Interview Puzzle

Friend 2 must have taken top 15 cards from the pile and reversed them. Now there are two piles, one with 15 cards and one with 37 cards and both of them will obviously have the same number of inverted cards.

If you want to understand mathematically, let us say that there were x inverted cards in the top 15 cards of the deck. Then the remaining 37 cards will comprise of 15-x number of inverted cards.

If we reverse the 15 cards the number of inverted cards will become 15-x and the number of inverted cards will be same in both the piles.

#396 - Link Chain Puzzle

As you see in the picture, there are four 3-link chains. All you have to do is join them into a big 12-link chain. For joining two closed links, one of the links must be cut and placed onto the other link for closing.

How many minimum links will you have to cut to make the big chain ?

Link Chain Puzzle

Just 3.

Refer the picture. All you have to do is cut three links from a single 3-link chain and then you can use them to join three other 3-link chains to make a big 12-link chain

#397 - Clever Logic Riddle

A dying old man wants to divide his entire land between his only two sons. Since his only wish is to treat them as equal as both of them have been too good to him, he wants to divide his land equally between them. The problem is that the land is significantly irregular in shape and thus there is no choice of cutting them in two equal halves.

Can you help him divide the land in a manner that both of his sons will be happy ?

Clever Logic Riddle

All he need to do is ask one of his son to divide the land in two part and tell him that the other son will have the choice of selecting one of those two halves.

In this manner both of them will be happy.

#398 - Hard River Crossing Logic Puzzle

You must have heard of so many river crossing riddles however this one is a bit tricky one. We have a dysfunctional family on one side of the river which includes mom and 2 daughters, dad and 2 sons, a maid and a dog. Like usual, there is a boat that can hold only two persons at a time (dog counts as one person as well). Obviously, the kids can’t operate the boat and we need an adult for that task.

Here comes the difficulties. The maid must remain with the dog so she can control it or it will head up for a violent biting. The dad cannot be left with the daughters without mom and nor can the mother be left alone with the sons without dad.

Can you help them cross the river?

Hard River Crossing Logic Puzzle

Suppose that everyone is standing at A corner and they have to reach the B corner

Let the housemaid and Dog go to corner B first and housemaid returns back to corner A.

Next, the housemaid and the first son go to B and she comes back along with the dog.

Now the father and the second son go to B and father comes back.

Mother and Father go to B and the mother comes back.

Housemaid and Dog go to B and the father comes back.

Father and mother goes to B and Mother returns back.

Mother and first daughter go towards B, Housemaid and Daughter returns back.

Housemaid and second Daughter go to B and Housemaid comes back.

Housemaid and Dog goes to B.

So, everyone has reached the other side of the river successfully.

#399 - Tricky Math Logic Problem

A girl was fond of collecting rare stamps. When she was twenty years old, she bought a box to collect her stamps. On her every birthday, she put 250 stamps in it and her sister who was also fond of collecting stamps took out 50 stamps from it on her birthday. The girl met an accident when she was 60 years old. When her box was opened, there were only 500 stamps in it.

How is it possible logically?

Tricky Math Logic Problem

The girl was born on 29 February, thus she put 250 stamps every four years.
In forty years, she put stamps only 10 times which makes the total of 2500 stamps.
Her sister was born on any other day and she took out 50 stamps from the box forty times which makes the total stamp she took out to be 2000.

Thus after forty years, the girl’s box had only 500 stamps.

#400 - IAS Logic Problem

Anabelle is a clever trader of rare artifacts. Each day she carries three boxes with each filled with thirty artifacts. The boxes cant hold more than that. She travels far of northern lands to sell these artifacts but on way, she comes across thirty checkpoints where she has to shed one of the artifact for each sack to the authorities for letting her pass.

How many artifacts will be left with her when she reaches her destination crossing all the check points ?

IAS Logic Problem

Anabelle is no dumb trader and she knows the strategy with the help of which she will be able to save 25 artifacts even after passing 30 check points.

All she will focus on is getting rid of the boxes as soon as possible.

To shed the first sack quickest possible, she will start filling artifacts from one box to other two. Assume that she is able to do that after passing through A check points.

(Space in first box) A + (Space in second box) A = (Remaining artifacts in third box) 30 -A
A = 10

Therefore, after 10 check points, she will be left with two boxes with 30 artifacts each. Now to get rid of the second box, she will start filling artifacts from second box to first box. Let us assume that she is able to get rid of the second box after B checkpoints.

(Space in first box) B = (Remaining artifacts in second box) 30 - B
B = 15

Therefore, after fifteen check points, she will be left with one sack with thirty artifacts in it.

Since she has five more check points left, she will have to give five more artifacts and after passing them all, she will still have 25 artifacts.