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?

Find out the missing number in the picture attached:

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

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

Can you discover the missing number in this series?

37, 10, 82
29, 11, 47
96, 15, 87
42, ?, 15

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

See the given image carefully. What you have to do is move the blue checkers in the position of the black checkers and vice versa. You are only allowed to move the checker to an adjacent empty space. Do it in the least possible moves.

I always drive my customer away.

Who am I?