Good Riddles

Question: A man is found murdered on the ground with 53 bicycles scattered around the room.

How did he die?

Question: If a white house is white and a yellow house is yellow, what color is a green house?

Question: What is the only question you can't answer yes to?

Question: When is 1500 plus 20 and 1600 minus 40 the same thing?

Question: You find me behind the stars; or in a sixth, seventh, or third.
It takes something round, a computer, and me to make pie.
I am bigger than anything you can think of.

What am I?