1. The problem statement, all variables and given/known data I need to prove that the least common multiple operation is associative. 2. Relevant equations 3. The attempt at a solution Pages of crappy algebra trying to use the fact that LCM(a,b) = |ab|/gcd(a,b) I hate to be "that guy" that doesn't post much of an attempt but I am getting nowhere with this. Maybe a hint or a fact about the LCM that will lead to a proof..?