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February 26, 2015

Which Letter is Missing ?

Which letter is missing from this sequence:

A , A , A , A , _ , A , A , A , A , A , A ,U

Note: the answer is not A or U.

February 25, 2015

Pick a Good Candy !

How do you place 50 good candies and 50 rotten candies in two boxes such that if you choose a box at random and take out a candy at random, it better be good!
That means probability of choosing a good candy should be highest. There is no restriction in putting the candies in 2 boxes. Any number of candies can be put in any box.

February 24, 2015

World with All Girls !!

In a world where everyone wants a girl child, each family continues having babies till they have a girl.
What do you think will the boy to girl ratio be eventually?
(Assuming probability of having a boy or a girl is the same)

February 23, 2015

Playing with Invisible Dice

You have 2 dice. One regular die and a an invisible die. Numbers 1 to 6 are written on the regular die.But you don't know what's written on the invisible dice.
After tossing both, I speak the sum of outcome of both die. It so happens that the outcome is always an integer between 1 to 12, with equal probability (1/12 each).
Can you guess what are the numbers printed on special invisible dice?

February 19, 2015

Alex bought a bag of apples

Alex bought a bag of apples on Saturday, and he ate a third of them. On Sunday he ate half of the remaining apples.
He ate one more on Monday and one more on Tuesday, and then ate half of the remaining apples on Wednesday. On Thursday he looked in the bag and saw that there was just one apple left.
How many apples did the bag have to begin with?

February 18, 2015

Spiderman's Girlfriends

Spiderman has two girlfriends, Mary Jane & Gwen Stacy.
After completing every mission, he rushes to the central subway. Since spidey is a nice man, much impartial, he takes which-ever train arrives first. From subway, one series go towards Mary's place, and another series move towards Stacy. Trains from either series appear every 10 minutes. Also, Peter Parker sticks with the train which arrives first.
But somehow, he notices that he is spending 9 times more dates with Mary Jane than Stacy. Can you explain why?

Add the Missing Numbers

Put the numbers 6, 10 and 12 to the correct place in the below sequence and make it complete.

1,  2,  4,  5,  9,  3,  7,  8,  11

February 10, 2015

Which of the Triangles fits the Missing Triangle?

Probability of Secret PIN

Suppose everyone in the class chose a secret 3-digit PIN number. What is the probability that everyone chooses a different number? Assume there are 120 students in the class.

February 7, 2015

Three Choices with One Coin

At a restaurant, how could you choose one out of three desserts with equal probability with the help of one single coin?

February 5, 2015

Who is the man's Sister?

A man escapes from jail with help from his girlfriend. Four girls are accused of being the man's girlfriend. His girlfriend is lying. Two girls are innocent and telling the truth. The other girl is the man's sister who is helping the girlfriend lie. Who is the man's sister?

Amanda: "Melinda is his girlfriend."
Vanessa: "Eva is lying."
Eva: "Amanda is lying."
Melinda: "Vanessa is not his sister."

February 2, 2015

Birbal Puzzle: Who was the real king ?

The King of a distant land had heard that Birbal was one of the wisest men in the East and so desired to meet Birbal. He sent Birbal an invitation to visit his country.

In due course, Birbal arrived in the distant kingdom. When he entered the palace he was flabbergasted to find not one but six kings seated there. All looked alike. All were dressed in kingly robes. Who was the real king?

The very next moment he got his answer. Confidently, he approached the king and bowed to him.

How did Birbal know who was the real king?