When finding the surface area of a composite figure, why is it often necessary to subtract sides common to each individual shape? complete the explanation.

identifiable shapes that are easy to find the (volume/surface area) of in composite figures will often have portions that overlap with each other. after finding the surface area of each individual shape, simply adding these surfaces areas together will result in a number (greater/less) than the real surface area. this means that after adding the surface areas of the individual shapes, it is necessary to (add/subtract) sides common to both shapes to get the true surface area.