If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?

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?

You can see it everyday, But cannot touch it at will. What is it?

What is the next number in this series?

4,12,84,3612....

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

There is a number which when you multiply by 3 and subtract 2 from the result, then the resulting number is the reverse of the actual number.

What is the smallest number that stands true on the statement?

If a shopkeeper can only place the weights on one side of the common balance. For example, if he has weights 1 and 3 then he can measure 1, 3 and 4 only. Now the question is how many minimum weights and names of the weights you will need to measure all weights from 1 to 1000? This is a fairly simple problem and very easy to prove also.

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

I can write cow in 13 letters.

Can You?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?