what's the probability of getting a king or a queen from a pack of 52 cards?

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.

Prove that twice of ten is the same as twice of eleven.

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 10 matches are played in total, how many players participated?
(b) If 20 players took part in the tournament, how many matches were played?

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

I know there are two methods by using three time the same number with a plus(+) operator , you can make sum as 60.

One of them is 20+20+20.

whats the other way ?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

What is the fastest way to double your money?

How can you make number one disappear by adding something to it?

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?