Question: Three cubes of sides l, 2l, and 3l are placed next to one another (in contact) with their centers along a straight line and the l=2l cube in the center. What is the position, along the line, of the CM of this system? Assume the cubes are made of the same uniform material. My reasoning: So the equation for CM= M1XI +M2X2 + M3X3/ TM ... where M= mass, and X= distance ....So M(l +2l +3l)/3m = CM M(6L)/3m = 2L So, I got the center of Mass is 2L I dont think my answer is correct, and even if my approach is correct. It is labeled a pretty easy problem, but I get really confused with problems without numbers. Also, I am not sure if you can conclude the total mass is 3M considering that means all the cubes would have to be the same mass .... and I also do not know what the question maker meant when he wrote the l=2l cube in the center ..... Please help!