Bill is a lovely boy. He likes playing football very much. He often comes back home between 4 p.m. and 5 p.m. One day, he comes back late. His mother says, "You come back home late today, Bill". "Yes, we have a new teacher. He is a math teacher," Bill answers.

    "How is he?" his mother asks. "I don't know. I think I can't believe him." "How is that?" his mother says. "One moment he says two and three is five and the next moment he says one and four is five," Bill answers.