Why Aeroplane windows are round?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

What number do you get when you multiply all of the numbers on a telephone's number pad?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

A donkey is behind another donkey
I'm behind that second donkey
But there is a whole nation behind me

It is a murder you can describe in a word.

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

How can you make number one disappear by adding something to it?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?