What happened when the wheel was invented?

What can you hold in your right hand, but never in your left hand?

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?

what does the below rebus means?

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??

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:

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

Which is the correct shadow of the bird?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

What does the below mathematical rebus mean?