John and his wife were living in a rural place. On a particular day, John's wife fell ill and he called the local doctor. When the doctor picked up, he said, "Doctor, my wife is ill. She might have appendicitis."

"This can't be possible! I took out her appendix two years ago myself," the doctor explained.

When diagnosed, John's wife was found to have appendicitis. How can this be possible?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

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?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

Below is the sum of symbols in each row and column in the figure. Analyzing the figure, can you find out the value of the symbols?

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

Where do fish keep their money?

Which tank will fill first?

What makes this number unique: 8,549,176,320?

How can a man go eight days without sleep?