Okay this seems like a really simple question. Basically I'm adding together 8 spheres (like raindrops coalescing into one bigger drop) and I'm getting two different answers for the new radius. Each individual drop is identical. I start by expressing the new volume in terms of the individual drops' radii, and then the new radius. The individual drops' radii are R. Volume = (4/3)∏(R)^3 * 8 = (4/3)pi(Rf)^3 I work it all out and find that the new radius is 2 times the radius of an individual drop. This is true according to a solution given. But when I try this with surface area.... S.A. = 4∏(R)^2 * 8 = 4∏(Rf)^2 4∏ cancels, then the new radius comes out as R*2*√(2) What am I missing here? Is Surface area not additive, or am I making some calculation error?