Edit or’s note: In light of the recent death of Martin Gardner, we are republishing this article from the August 1998 issue of Scientific American. Gardner wrote the "Mathematical Games" column for Scientific American from 1956 to 1981 and continued to contribute columns on an occasional basis for several years afterward . This article, which includes four puzzles by Martin Gardner, was his final piece for the magazine.
My “Mathematical Games” column began in the December 1956 issue of Scientific American with an article on hexaflexagons. These curious structures, created by folding an ordinary strip of paper into a hexagon and then gluing the ends together, could be turned inside out repeatedly, revealing one or more hidden faces. The structures were invented in 1939 by a group of Princeton University graduate students. Hexaflexagons are fun to play with, but more important, [...]

Original post by Scientific American Topic - Exercise and Fitness