What occurs twice in a week, once in a year but never in a day?

Which tank will fill first?

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?

Cristina was born in 1888. She just had her 30th birthday today how did that happen?

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

In a football game, Christina defeated Teresa by 2 - 0 but no man from either side scored. How can this be possible?

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

There is a square piece of paper with a hole that is denoted by the circle on the top right side in the given picture. You have to cut the paper in a manner that it forms two and only two separate pieces of paper and then rearrange the pieces in a manner that the holes come in the centre of the paper.

A thief enters a store and threatens the clerk, forcing her to open the safe. The clerk says, “The code for the safe is different every day, and if you hurt me you’ll never get the code.” But the thief manages to guess the code on his own. How did he do it?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?