1. The problem statement, all variables and given/known data Determine the moment of inertia of the cross sectional area of the T beam with respect to the x' axis passing through the centroid of the cross section.(I'm attaching a diagram) 2. Relevant equations 3. The attempt at a solution Hi! I'm having a little trouble with this problem. I've already calculated the centroid with respect to y to be 60 mm. Ix'=Ix+A(dy)2 Ix'=(1/12)(150)(303)+(150)(30)[(150)(30)(60-15)] What I don't understand is how they are calculating dy! Could someone please explain to me what they are doing?