As already pointed out, the article has the "1/3 should be 1/2" correction; and its statement that 8/15 = 4 * 2/5 is a bit of an exaggeration. But in the boys and girls problem, knowing that boys and girls are equally likely is not sufficient information to solve the problem. It might be that the probability of having same-sex siblings is significantly greater than (or less than) 1/2. In actuality, I suspect it is significantly greater than 1/2. The determination of the gender of a child includes a number of factors that are specific to its parents, including such things as genetics and sexual practices. For example, didn't Henry VIII's wives have some problem with that? --ms Andy Latto wrote:
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-04C7-1270-8 4C783414B7F0000 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
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