Why do we preferably have round manhole covers and not square ones?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

In Greek mythology, the Sphinx sat outside of Thebes and asked this riddle of all travellers who passed by. If the traveller failed to solve the riddle, then the Sphinx killed him/her. And if the traveller answered the riddle correctly, then the Sphinx would destroy herself. The riddle:

What goes on four legs in the morning, on two legs at noon, and on three legs in the evening?

Oedipus solved the riddle, and the Sphinx destroyed herself.

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

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

What demands an answer, but asks no questions

If eleven plus two equals one, what does nine plus five equal?

Identify Me

Hint1: I am a god
Hint 2: I am a planet
Hint 3: measurer of heat

A generous owner of a company decided to give a bonus of $45 to every man and $60 to every woman on his birthday. But only one-ninth of the men and one-twelfth of the women were present to take the bonus.

Can you calculate the amount of money the owner spent if there were 3552 employees?

I am an odd number. Take away a letter and I become even. What number am I?