Recreational mathematics"" -- tricks, stunts and unusual phenomena which you do to amuse (or confuse) your friends. This sort of intellectual legerdemain is always fun and there are all kinds of different posers, from formulae which will enable you to guess someone's age, to telepathy and divination, to the limitation of Houdini's famous coat escape. Only a few simple props are necessary -- cards, coins, paper, etc. Fine for any age -- once you're able to rack up a 600 or so on your P.S.A.T.