This is a problem from my abstract algebra book written by Ted Shifrin: A druggist has the five weights of 1, 3, 9, 27, and 81 ounces, and a two-pan balance. Show that he can weigh any integral amount up to and including 121 ounces. How can you generalize this result? While I see how it's possible to obtain lots of different weights with these 5, I have absolutely no idea how I can generalize my result. Does anyone know the answer to this problem? Thanks a lot in advance.