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

In which direction should the missing arrow point?

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

No one wants to have it, but if one got it, he does not want to lose it. What is It?

By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

What does below chemistry rebus means?

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.

One night, a man runs away from home. He turns left and keeps running. After some time he turns left again and keeps running. Later, he turns left one more time and runs back home—but when he gets home, he finds a man in a mask. Who was the man in the mask?

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?