Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

Find the missing number in the series below

13 -21 34 -55 ? -144

My location can be determined by the below rebus.
So where am i ?

If a wheel has 54 spokes, how many spaces are there between the spokes?

There are two guys standing face to face in a room. On a wall, there is a clock. One of those is a prophet. He tells the other guy that he will be stabbed in the back in five minutes.

Shocked to hear that, the other guy stares at the clock. Just after the five minutes, he is stabbed on the back. Can you tell what happened?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?

Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

There is a place where if I stand up straight, I will still be considered sideways.