Move four matchsticks to the below square to form three squares?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

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?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

Count the number of squares in the picture below.

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

What happened when the wheel was invented?

Jack was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

There are two guys standing face to face in a room. On a wall, there is a clock. One of those is a prophet. He tells the other guy that he will be stabbed in the back in five minutes.

Shocked to hear that, the other guy stares at the clock. Just after the five minutes, he is stabbed on the back. Can you tell what happened?