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

What does this simple rebus mean?

John gave half of the apples he had plus one more to Jacob. He gave half of the remaining ones plus one more to James. Now, John was left with just one apple.

Can you find out how many did he have in the beginning?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

Which alphabet is a part of our body?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

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?

You walk into a room where there are three primates held in their respective cages:
1) A lion who is eating the flesh of a goat.
2) An orangutan who is playing with blocks.
3) A donkey who is sitting idle.

Who is the most intelligent primate in the room?

By what process could you make a 'Tea-Table' into food?

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?