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

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?

A Monkey, a squirrel, and an Eagle are racing to the top of the mango tree. Assuming all these animals are in perfect shape, Which animal will reach to Banana first?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.