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

If eleven plus two equals one, what does nine plus five equal?

Using eight eights and addition only, can you make 1000?

What jumps when it walks and sits when it stands?

If a boy blows 18 bubbles,
Then pops 6 eats 7 and then
He pops 5 and blows 1.
How many are left?

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?

Different lights make me strange by changing me into different sizes. What am I?

I look at you, you look at me, I raise my right, you raise your left. What am I?

He runs but never walks. Murmurs, but never talks. Has a bed, but never sleeps. And has a mouth, but never eats?

What word begins and ends with an E, but has only one letter?