Solutions of Advanced Problems

Solution by Gregg Patruno, Staten Island, New York. Variations of this 'advanced' problem seem to appear endlessly (e.g., International Mathematical Olympiad, 1972, U.S.A. Mathematical Olympiad, 1975, and Monthly Problem E3107, 1985). It seems that many problemists have not yet discovered a simple graphical method that dispatches them with little effort. The following should put this tired old problem to rest.