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?

Find the next number in the sequence

5 12 24 36 ?

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

If eleven plus two equals one, what does nine plus five equal?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

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

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

John and his wife were living in a rural place. On a particular day, John's wife fell ill and he called the local doctor. When the doctor picked up, he said, "Doctor, my wife is ill. She might have appendicitis."

"This can't be possible! I took out her appendix two years ago myself," the doctor explained.

When diagnosed, John's wife was found to have appendicitis. How can this be possible?

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?