Logic Riddles

Question: A man has 3 children and half of them are girls, how is this possible?

Question: How can you throw a ball 20 meters, and have it come back to you without hitting anything?

Question: You are a surgeon who has to perform 3 operations today, but you only have 2 pairs of gloves (a and b) to perform the operations. Each of the people you are performing surgery on are infectious so you cannot touch any of them or their bodily fluids and they can't touch each other's bodily fluids. How do you perform all 3 operations with only 2 pairs of gloves?

Question: There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.