#361 - Tough Probability Interview Question

There is a country where everyone wants a boy. Every family continue to have babies till a boy is born. If the probability of having a girl or a boy is the same, what is the proportion of boys to girls after some time in that country?

Tough Probability Interview Question
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Since the probability of having a girl or a boy is same, half of the families will have a boy first and stop. The other half of the families will have a girl and from half of those families, the second born will be a boy and they will stop while the others will again have a girl. This process will continue.

Suppose the number of couples are N, the number of boys will be N.

1/2 have a boy and stop: 0 girls
1/4 have a girl, then a boy: N/4 girls
1/8 have 2 girls, then a boy: 2*N/8 girls
1/16 have 3 girls, then a boy: 3*N/16 girls
1/32 have 4 girls, then a boy: 4*N/32 girls
…
Total: N boys and
1N 2N 3N 4N
– + – + – + — +… = ~N

Therefore the proportion of boys to girl will be quite close to 1:1.

#362 - Short History Riddle

October Revolution is well know in russian history. Which month do they celebrate it ?

Short History Riddle
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November, Their calandar was 13 days behind ours.

#363 - 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
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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.

#364 - Hard Math Sequence Puzzle

Find the next number in the sequence ?

2 3 3 5 5 4 7 5 11 6

Hard Math Sequence Puzzle
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13 8 its prime number and then number of letter in prime number

#365 - 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
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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.

#366 - Trickiest Primates Riddle

You walk into a room where there are three primates held in their respective cages:
1) A lion who is eating the flesh of a goat.
2) An orangutan who is playing with blocks.
3) A donkey who is sitting idle.

Who is the most intelligent primate in the room ?

Trickiest Primates Riddle
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You are also a primate and you are human thus you are the most intelligent.

#367 - Trick Logic Riddle

Alex is asked to stand behind Ryan and Ryan is asked to stand behind Alex. Both of them feel confused about it and don’t know what to do?

But it is quite possible, do you know how?

Trick Logic Riddle
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If Alex and Ryan stand back to back, then they can make it possible.

#368 - Counting Chess Squares Puzzle

How many squares are there in a chess board ?

Counting Chess Squares Puzzle
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204

#369 - Famous Trivia Puzzle

Can you tell a 3D object that actually has just two surfaces?

Famous Trivia Puzzle
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Did you think of paper?
Well that will be a wrong answer as a piece of paper has 6 surfaces as the edges are also counted as surfaces only no matter how thin they are.

The correct answer is a cone.

#370 - 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
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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.