How can a man go eight days without sleep?

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

Below toothpicks/matchsticks indicate the group of fishes moving from west to east direction. Can you make them move from east to west by just moving three toothpicks/matchsticks?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

No matter how little or how much you use me, you change me every month. What am I?

Given that

(78)^9 = 6
And (69)^4 = 11

Can you find out

(99)^2 =?

(Note: This is Logical, not Mathematical)

Which tank will fill first?

The sum of a mother, her baby and her dog's weight is 170 Kg. How much does the baby weigh if the mother weighs 100 kg more than the combined weight of the baby and the dog, and the dog weighs 60 per cent less than the baby?

On her drawing table, Sayna lit 12 coloured candles. A few seconds later she blew two candles off.

How many candles Sayna have at the end?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?