Logic Riddles

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

Question: A man in prison has a visitor. Afterward a guard asks the inmate who the visitor was to him. The inmate replies: "brothers and sisters I have none, but that man's father is my father's son." Who was the visitor to the inmate?

Question: There was once three trees. The first tree did whatever the third tree did, and the third tree did what ever the second one does. What happens if tree number two gets cut down?

Question: Four cars come to a four way stop, all coming from a different direction. They can't decide who got there first, so they all go forward at the same time. They do not crash into each other, but all four cars go. How is this possible?

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