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

A man dies of old age on his 25 birthday. How is this possible?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

How many times can you subtract the number 5 from 25?

Which English verb becomes past tense just by rearranging the letters?

What runs around the whole yard without moving?

You have an empty wine bottle with a cork that has been secured at the top in a normal way. There is a metal ring inside the bottle that is suspended by a string.

How can you make the metal ring drop to the bottom if you are not allowed to touch anything - not the bottle, not the cork, not the thread and not the ring?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1