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

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?

The centre of the third figure is empty. What digit should fit inside?

The ages of a father and son add up to 66.
The father's age is the son's age reversed.
How old could they be?
(3 possible solutions).

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

Move three sticks of the spiral below to form a square.

You’ll find me on Mercury, Earth, Mars, Jupiter, Saturn, and Uranus. But never Neptune, or Venus. What am I?

A word I know has six letters it contains, remove one letter and 12 remain. What is it?