Square Division

Show how to divide a unit square into two rectangles so that the smaller rectangle can be placed on the larger with every vertex of the smaller on exactly one of the edges of the larger.

Source: 1994 Dutch Mathematical Olympiad; as reported in Crux Mathematicorum, Sept 1998, Vol. 24, No. 5, p. 264.

This problem was sent recently as a Macalaster Problem of the Week (#887). The solution was sent with the following week's puzzle, but no derivation was included, so I thought it was worth seeing if some of my readers could derive the solution.

Mail to Ken