Replace the question mark with the correct number in below Picture:

Doctor Alex and a bus driver John are both in love with the same woman named Olivia. The bus driver need to go for a long trip of 10 days, Before he left he gave Olivia 10 apples.

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

I am white when I am dirty, and black when I am clean. What am I?

What do you get if you add 2 to 100 four times?

In the picture, you can see a chess board. On the top left position, the K marks a knight. Now, can you move the knight in a manner that after 63 moves, the knight has been placed at all the squares exactly once excluding the starting square?

What has many teeth, but cannot bite?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

At my favorite fruit stand,
an orange costs 18,
a pineapple costs 27,
and a grape costs 15.
Using the same logic, can you tell how much a mango costs?

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?