What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Who is that with a neck and no head, two arms and no hands? What is it?

A train leaves from point A for point B at 80 mph. After half an hour, another train leaves from point B for point A at 60 mph.

Which of the trains will be farther from point A when they meet ?

Intelligence Agency need to break the vault but the problem is that they are not able to break the vault.

On the vault, a text is written as:

31 11 33 33 43 45
21 25
31 24 11 31 51 41

To Break the code Intelligence Agency brings a mathematician named Joseph.
Minutes later he deciphers the code.

Whats the code?

What is both possible and impossible at the same time?

I look at you, you look at me I raise my right, you raise your left. What am I?

The day after tomorrow will be three days before Tuesday. Can you find out what is today?

Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

No one wants to have it, but if one got it, he does not want to lose it. What is It?