1. The problem statement, all variables and given/known data Find the coordinates for the center of mass in the picture above. Plate is uniform. 2. Relevant equations Since it's uniform, the lengths can be converted to the mass. So: coord x =(M1X1 +M2X2 + M3X3 + ... +MiXi)/(M1 +M2 + M3 + ... +Mi) coord y =(M1Y1 +M2Y2 + M3Y3 + ... +MiXi)/(M1 +M2 + M3 + ... +Mi) I saw it as 3 pieces: the original square, 6x7, and two missing pieces, 2x2 and 4x4. I'll only put the X equation since Y is similar. s = plate (shown) 1 = 4x4 missing piece 2 = 2x2 missing piece. I simply need to find Xs = coords of the plate. coord x (total, 6x7 square) = 1 = (MsXs +M1X1 + M2X2) / (Ms +M1 + M2) (Ms +M1 + M2) * 1 = (MsXs +M1X1 + M2X2) Ms +M1 + M2 - M1X1 - M2X2= MsXs Ms/Ms +M1/Ms + M2/Ms - M1X1/Ms - M2X2/Ms = Xs Plugged in the values, it didn't come out correctly. Same for the Y coordinate. Edit: Ms/Ms +M1/Ms + M2/Ms - M1X1/Ms - M2X2/Ms = Xs 22/22 + 16/22 + 4/22 - (16/22 (2)) - (4/22 (3)) = -0.090 However, answer given is -0.90 3. The attempt at a solution I was shown the solution of cutting up the plate into 4 pieces, and finding the CM that way. That came out correct. But I want to know what went wrong when I went 'take whole plate, remove two pieces, find CM' There's probably something really obvious that I'm missing.