Which number should replace the question mark?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

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?

Why is Saturday stronger than Monday?

Solve the equation in the image by looking at the pattern closely.

Do you know of a place where the wind blows south and then suddenly shifts direction towards the north?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Which digit occurred maximum times between the number 1 and 1000?

The dirtier I get, the whiter I look. Who am I?