Can anyone tell me a word in the English dictionary which has a silent 'z'?

What do you get if you add 2 to 100 four times?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

John was gifted a new Hayabusa. He drove x miles at 55mph. Then he drove x+20 miles at 40mps. He drove his bike for 100 minutes. How much distance did he travel?

What is common among 11, 69, and 88?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

A man is looking at a photograph of someone. His friend asks who it is. The man replies, “Brothers and sisters, I have none. But that man’s father is my father’s son.” Who was in the photograph?

I was born in a small house and I live in it all alone. No windows and no doors have been assigned to my house. The only way I can go out is by breaking through the walls of my house.

Who am I?

Find the value of "?" in the ball picture Riddle below:

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?