When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

What has many teeth, but cannot bite?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Which is heavier: a ton of bricks or a ton of feathers?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

What does an Island and the letter T have in common?

I am sure no one can have two things for dinner. what are they?