Question: You were at a carnival. You had four tickets and one ride was four tickets. Once you were done, you didn't buy anymore tickets and you had one ticket left. How is that possible?
Answer: You played a game for three tickets, I didn't say games costed four tickets.
Question: A semi truck weighing exactly 10,000 pounds gets onto a bridge that is 100 miles long. The bridge's weight limit is exactly 10,000 pounds, any more will break the bridge. After going about 80 miles down the bridge a small bird lands on the truck.
Answer: Nothing, after traveling 80 miles the truck will have surely burnt enough fuel to allow the bird to land on the truck without breaking the bridge.