The Magic Number
On a piece of paper write down the number 12345679. Do not include the figure 8. Then ask a friend to choose any number from 1 to 9. He must tell you this number. Now you have to multiply his number by 9 in your head; that is, do not tell your friend what you are doing. Write this multiplication under the “magic number.” For example, your friend might choose the number 3. You then multiply 3×9 in you head, and you write the number 27 under 12345679. When your friend multiplies these two number, he will be quite surprised. In fact, it will be difficult to believe. The answer will be all 3’s, the number he chose. (In this example, the answer will be 333,333,333.) For practice, try it with other number before you try this “multiplication magic” on a friend.