A man dies of old age on his 25 birthday. How is this possible?

Imagine you are in a room with no windows or doors. How will you get out?

You need to move three matchsticks to form three squares. Can you do it?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

You are given 16 witch hats. The hats are divided in four different colours – red, blue, green and yellow. Every colour has been assigned to four hats. Now each of the hat will be glued with a label of an arithmetic sign – ‘+’, ‘-‘, ‘x’ or ‘/’. But you can label one sign only once on one colour. In such an arrangement, the hats can be uniquely defined by its colour and symbol.

Can you arrange all the 16 hats in a 4x4 grid in a fashion that no two rows and columns have a repetition of colour or sign?
We have arranged four hats in the below picture to assist you.

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

Explain how?

What happened when the wheel was invented?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

Rearrange the letters in "new door" to make one word.