[math-fun] Tiling a square

Hi all, I know that 7 * 5^2 + 9 * 3^2 = 16^2, which suggests that 7 5x5 squares plus 9 3x3 squares can possibly tile a 16x16 square. Is there a relatively simple way to figure out if either: a) no, they won't, or b) yes, and here's how? Ideally, I'd like to learn the process, not just the answer, as I will probably have other combinations to consider. Thanks, Kerry Mitchell -- lkmitch@gmail.com www.kerrymitchellart.com