Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

What has many keys but can’t open a single lock?

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

What has to be broken before you can use it?

Prove that twice of ten is the same as twice of eleven.

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

What does below pictogram mean?

What can go up a chimney down, but can’t go down a chimney up?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n