You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer and a five-minute timer, how can you boil the egg for only two minutes?

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle:

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?

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

What am I?

I look at you, you look at me, I raise my right, you raise your left. What am I?

Can you place six X (crosses) in below board without making three in a row in any way ?

Whats the next number in the below number sequence pattern.

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

People make me, save me, change me, raise me. What am I?