The problem that has just been discussed has much to recommend it. It is, first of all, a problem since it requires such heuristics as the following: solving a simpler problem, making a picture or chart, looking for patterns, making tables, making predictions(guessing), generalizing the patterns, and working backward. The problem also embodies numerous concepts of mathe- matics, including prime numbers, compos ite numbers, factors, multiples, common factors, common multiples, greatest com mon factor, least common multiple, square