What is the next number in this matchsticks series riddle?

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

A man looks at a painting in a museum and says, “Brothers and sisters I have none, but that man’s father is my father’s son.” Who is in the painting?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

Which tank will fill first?

As you can see that fifteen matches have been used to form an arrangement. What you have to do is remove any six of them to make them ten.

How far can you walk into the woods?