Why do you find that most of the buildings are deprived of the 13th floor?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

What is the fastest way to double your money?

In the picture, you can see a chess board. On the top left position, the K marks a knight. Now, can you move the knight in a manner that after 63 moves, the knight has been placed at all the squares exactly once excluding the starting square?

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

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

What has one letter and starts with an E?

Why blonde cannot dial 911?