Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

The husband and wife were jogging in the morning. To match every two steps of the husband, the wife required three steps. If Both of them start with the here right foot. After how many steps do their left foot be together?

Why is 6 afraid of 7?

This is a famous paradox which has caused a great deal of argument and disbelief from many who cannot accept the correct answer. Four balls are placed in a hat. One is white, one is blue and the other two are red. The bag is shaken and someone draws two balls from the hat. He looks at the two balls and announces that at least one of them is red. What are the chances that the other ball he has drawn out is also red?

I look at you, you look at me I raise my right, you raise your left. What am I?

Count the Triangle in the figure given below:

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?

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?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

John had a bag containing colourful marbles. The colours are red, green and blue. The total number of marbles he had in his bag was 60. There are 4 times as many red marbles as green marbles. 6 more blue marbles than green marbles. How many marbles of each colour did John have?