A magician has a little money box which can contain one yuan or fifty cents coin.He asks for a one yuan and fifty cents coin from the audiences, then he turns around.A audience will choose one coin from the two according to his preference and put a coin into the box,and then put the box on the table tightly, then hide the other coin. The magician never touches the box but he can tell what coin is in the box according to telepathy.What a magical box!