Math Riddles

Question: sedentary stop + sudden start = ?

Question: 1 11 21 1211 111221 312211 13112221 1113213211 what comes next?

Question: A man wanted to enter and exclusive club, but did not know the password to get in. He waited by the door and listened. The doorman said "Twelve" and the other man said "Six" and was let in. A second member came up and the doorman said "Six" to which the member replied "Three" and was let in. The man went up and the doorman said to him "Ten" the doorman said "Five" but was not let in. Why?

Question: Why is 12 divided in half 7?

Question: What temperature is twice as hot as 0 degrees Celsius?