SIX TUMBLERS
Tom was playing with six tumblers. He had filled three of them with water and the other three were empty. ‘Look, they are full and empty one after the other,’ he said, ‘but I am going to make them so that there are three full ones, followed by three empty ones.’ At this point his mother was convinced that he would spill them, so she took them away, but in fact Tom had a very simple plan to make three full next to three empty. What was it?