Math Riddles

Question: what does 1+1=.

Question: sedentary stop + sudden start = ?

Question: Hard, Harder, and Hardest are brothers. By age from youngest to oldest, it goes Hard, Harder, Hardest. Hard is half the age of Hardest who is 20 which means hard is 10. Harder has a two-year difference between the number of years older he is than Hard and the number of years younger he is than Hardest. Harder is closer to the age of Hard than Hardest. How old is Harder?

Question: Two men find an old gold coin and want to have a coin toss with it to decide who gets it. The only problem is the coin is heavier on one side so it comes up heads more than tails. What is a fair way for the men to toss the coin and decide who gets the coin?

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?