Mensa is a society open to anyone scoring in the top 2% on a number of different exams. This corresponds to a 1250 on the older SATs; the newer SATs are not accepted for membership. For more information on joining, see below.
Solutions to the July 2000 Think & Derive (dvi,pdf) puzzle column; the 2nd puzzle also appeared in the January 2001 issue of Mensa's national Bulletin.