What occurs twice in a week, once in a year but never in a day?

Move four matchsticks to the below square to form three squares?

There was a blind man. He had four socks in his drawer either black or white. He opened it and took out two socks. Now the probability that it was a pair of white socks is 1/2.

Can you find out the probability that he had taken out a pair of black socks ?

A Child was born in Lahore, Pakistan.

Still child is not a Pakistani citizen.why ?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

A man died, leaving $10,000,000 for his widow, 5 sons and 4 daughters. Each daughter received an equal amount, each son received twice as much as a daughter, and the widow received three times as much as a son.

How much did the widow receive?

You are in a land where thirty men and two women were dressed in classic black and white dresses.
They begin to fight as soon as any of them move.

Where are you?

Can you spot the hidden girl in the picture below?

Manish has to secure 40% marks to pass his B.tech final exams.
He got just 40 marks and failed by 40-marks.

What is the maximum marks?

What is the fastest way to double your money?