What does this mathematical rebus means ?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Name a key which is hardest to turn.

As you can see that fifteen matches have been used to form an arrangement. What you have to do is remove any six of them to make them ten.

Can you count the number of matches in the picture below ?

What time is it when an elephant sits on a fence?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

French Police inspects a room where there are no windows, no doors, no tables and is almost empty expect there is just a puddle of water. They found a dead man who obviously hung herself from the ceiling, but they are not able to figure out how this had happened.

John and Jacob entered the crime scene and easily able to solve the case.

How did the man die?

John went to buy some expensive, foreign chocolates. He only had Rs 100 with him. When he reached the shop, he got out and know that on those chocolates, there was a 15% import duty and 5% VAT.

How much worth chocolate should he buy so that he can accommodate it in Rs 100?

What question can you never answer yes to?