Secret: Write 1089 on a piece of paper, fold it and place it on your table. Ask someone to choose any three digit number. All three digits must be different and the first must be higher than the last. Get them to reverse the whole number and write that underneath the first. If, for example, he chose 983 he now writes 389. The lower number is then subtracted from the other. The answer (which, in this example, is 594) is then reversed and this time the two are added together. Open the paper – your prediction is the same as the spectator's total. In fact, if the calculations are done correctly, the answer is always 1089!