What is the centre of gravity?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

What is the difference between a jeweller and a jailer?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

Your mother’s brother’s only brother-in-law is asleep on your couch. Who is asleep on your couch?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.

What English word has three consecutive double letters?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

A girl says this to her best friend: “I was born in 1955, and I celebrated my 17th birthday last weekend.” Her best friend thinks she’s lying, but she’s actually correct. How is that possible?

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