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?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

What has a ring but no finger?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

If one and a half boys, eat one and a half burgers in one and a half hours.

How many burgers can 9 boys eat in 3 hours?

Can you place three balls such that the equation shown in the picture holds true?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

Which word is least like the others? Third, fourth, fifth, sixth, seventh, eighth, ninth?

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?

Can you identify if it's a murder or a suicide ?