When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

What goes up but never comes down?

What is black when you buy it, red when you use it, and gray when you throw it away?

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

which number am I?

Use the numbers 2, 3, 4 and 5 and the symbols + and = to make a true equation. Conditions: Each must be used exactly once and no other numbers or symbols can be used.

A boy purchased a book from a bookkeeper and gave him $100.
The cost of the book is $50 but the bookkeeper has no change, so he gets the change from the next shop and returns the boy his $50.

After some time the next shopkeeper came with the $100 note and told the bookkeeper that the note was a fraud, so he took the money back.

How much loss did the bookkeeper face?

Can you count the number of squares in the given picture?

What is red and smells like blue paint?

Can you divide the below-given shape into four equal and identical pieces?

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?