Actually, the answer to question 3 also contains incorrect statement. 8/15 is not four times 2/5 (although it is greater). Additionally, to get the 1/2 result for question 4 implicitly depends on another assumption: boys and girls are equally likely to be playing in the yard. If, for example, we assume instead that two girls will always play together, then the probability that the other child is a boy is 1. Franklin T. Adams-Watters -----Original Message----- From: Andy Latto <Andy.Latto@gensym.com> I think the solution to the last of the probability puzzles on the Scientific American web site at http://www.sciam.com/article.cfm?chanID=sa010& articleID=000E3F5B-04C7-1270-84C783414B7F0000 is incorrect. But since this sort of puzzle is notoriously tricky to get right, I thought I'd check with fellow math-funsters rather than risk embarrassing myself with an incorrect letter to the editors. Andy Latto andy.latto@pobox.com ___________________________________________________ Try the New Netscape Mail Today! Virtually Spam-Free | More Storage | Import Your Contact List http://mail.netscape.com