Lets say I have n number of masses, x1, x2, x3,...,xn. How do I find the center of mass of the group of masses? I'm not really sure how to do this, but does it have something to do with having a test mass and finding the direction of the force and different points around the group of masses, and then finding where they intersect? (I'm not sure what maths this would involve too.) This isn't a homework question, I'm just curious as to how this can be done.