A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?

What kind of storm is always in a rush?

Solve this riddle by finding the odd one out from the rest.

What is the next number in this series?

4,12,84,3612....

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.

Prove that the below maths equation is true.

8 + 8 = 91

Which number should replace the question mark?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

How many triangles can you find in this given picture?

There is a box in which distinct numbered balls have been kept. You have to pick two balls randomly from the lot.

If someone is offering you a 2 to 1 odds that the numbers will be relatively prime, for example
If the balls you picked had the numbers 6 and 13, you lose $1.
If the balls you picked had the numbers 5 and 25, you win $2.

Will you accept that bet?