Good Riddles

Question: Mary gets in the shower, but surprisingly her hair is not wet when she gets out. How is this possible?

Question: what can go up a chimney down but cant go down a chimney up

Question: A man is twenty years old but has only had five birthdays. How is that possible?

Question: What starts with the letter "t", is filled with "t" and ends in "t"?

Question: If 1/2 of 5 is 3, then what is 1/3 of 10?