Can you count the number of quadrilaterals in the picture below?

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?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

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

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

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

Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

How old is your son? asked a man to his neighbour. My son is five times as old as my daughter and my wife is five times as old as my son. I am twice as old as my wife whereas my grandmother, who is celebrating her eighty-first birthday is as old as all of us put together.

How old is the man's son ?

What is the next number in the series?

15 29 56 108 208 ?

What has to be broken before you can use it?