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?

Can you count the number of triangles inside a triangle?

A man is trapped in a room. The room has only two possible exits doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

10 people came into a hotel with 9 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the tenth guest to wait for a little with the first guest in room number 1. So in the first room, there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, ..., and the ninth guest to room number 8. Then he returned to room number 1 and took the tenth guest to room number 9, still vacant.
How can everybody have his own room?

If 1+9+8=1, what is 2+8+9?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

What number comes next in this sequence:
7 8 5 5 3 4 4 _

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

why number 8549176320 is one of a kind?

Which of the eight images will fill the missing image in the puzzle below?