Puzzle of the Week for 15 March 1999

Twenty-four matchsticks can be arranged to form a grid of squares as in the picture. You may have seen a puzzle that asks if you can remove four matchsticks without moving any of the others, so that only five squares remain. If that's too easy, try to leave four squares, or six squares ... or three squares, or two squares. Can you leave seven or eight squares, or even nine squares? In each case, the rules are the same: you must remove exactly four matches, and the other twenty must remain in their original positions.