1. The problem statement, all variables and given/known data 2. Relevant equations This would be the part I think I'm missing 3. The attempt at a solution In the fourth line, Ix, where is the justification for multiplying 1/3 by the first term? I believe they are using the center of inertia of a rod, which is mr2 and the first term doesn't make much sense. Could someone explain to me the justification of that line?