How can you write nineteen in a manner that if we take out one, it becomes twenty?

Which wheel of car does not rotate when you turn your car right?

10+10 and 11+11 can give you the same answer.

Explain how?

How far can you walk into the woods?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

Below toothpicks/matchsticks indicate the group of fishes moving from west to east direction. Can you make them move from east to west by just moving three toothpicks/matchsticks?

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?

The more you take me, the more you leave me behind.
Who Am I?

Our product and our sum always give the same answer. Who are we?