Newsgroups: sci.math, rec.puzzles From: Dan Hoey Date: Thu, 24 Mar 2011 21:12:21 -0400 Subject: Re: One Through Nine, With Eight Missing, And Two Ones Leroy Quet wrote: > The solution -- except reflections and rotations -- can be seen to be > unique by first noting that, due to the evenness and oddness of the > numbers, the three even numbers must be in some order along a main > diagonal. Neat. So combining the two ideas (even diagonal and 9 triples) there are only nine cases, all but one of which yield quick contradictions. 2 9 7 2 9 7 4 9 5 4 9 5 6 9 3 6 9 3 9 3 6 9 3 6 9 5 4 . 4 . . 6 . . 2 . . 6 . . 2 . . 4 . 5 2 . 7 4 . 7 6 . . 5 6 . 3 4 . 7 6 . 3 2 . 7 4 . 5 2 4 . 7 2 . 5 2 . 3 Dan