Count the number of balls in picture below:

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

John needs to purchase 100 chocolates from three different shops and he has exactly 100 rupees to do that which he must spend entirely. He must buy at least 1 Chocolate from each shop.

The first shop is selling each chocolate at 5 paise, the second is selling at 1 rupee and the third is selling at 5 rupees.

How many chocolates should he buy from each shop?

A man says, "Brothers and sisters, have I none, but that man's father is my father's son." Who is that man?

You are confined in a room and given two metal rods. Out of these two rods, one is magnet and the other is the iron rod. They look starkly similar. You don't have any other metal object in the room.

How will you decide which one of those is magnet?

You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

What is the centre of gravity?