Good Riddles

Question: There is a 100 pound watermelon laying out in the sun. 99 percent of the watermelon's weight is water. After laying out for a few hours 98 percent of the watermelon's weight is water.

How much water evaporated?

Question: What always eats but is always hungry?

Question: What goes up when the rain goes down?

Question: At the sound of me, men may dream, or they may stamp their feet.
At the sound of me, women may laugh, or even weep.

What am I?

Question: Tom and Joe want to sit behind each other in class and the teacher arranges them so they are both happy.

How did the teacher do so?