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.

Can you find out the remainder when 3^300 is divided by 5?

There is something which you can be arrested for attempting but not for successfully completing.

Using eight eights and addition only, can you make 1000?

Which tank will fill first?

What is the next number in this matchsticks series riddle?

10+10 and 11+11 can give you the same answer.

Explain how?

Today is John's birthday.
A year ago, John had five candles and he lit all the candles except the one at the last.
Now he is going to light all the candles.

How old is John Today?

(He is not five today.....)

How do you go from 98 to 720 using just one letter?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?