When it's bad luck to meet a black cat?

Count the squares in the matchstick puzzle below?

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

It's a test that will check your IQ.

Suppose you have one 11 minute hourglass and one 13 minute hourglass.

Can you measure exactly fifteen minutes using them ?

See the given image carefully. What you have to do is move the blue checkers in the position of the black checkers and vice versa. You are only allowed to move the checker to an adjacent empty space. Do it in the least possible moves.

Count the number of squares in the picture below.

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

How far can you walk into the woods?

There is so small cabin inside a deep forest.
All the forest burned out to worst possible but the inside of the cabin is still the same.
However all the person inside the cabin die.

How come ?

Rectify the following equality 101 - 102 = 1 by moving just one digit.