Why is 6 afraid of 7?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

What number should come in place of the question mark below?

Can you divide numbers from 1 to 9 (1 2 3 4 5 6 7 8 9) into two groups so that the sum of the numbers of each group is equal?

Note: 9 cannot be turned over to make it 6.

Why is Saturday stronger than Monday?

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

A clock loses 10 minutes each hour. If the clock is set correctly at noon, what time is it when it reads 3 PM?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

what does this picture(rebus) riddle means ?