If there are 4 prisms together and touching, there are some hidden areas that don't make it out to the surface. Those areas should not be counted in the overall surface area. They should be subtracted.
Yesterday, Jake laid down 2/3 yards of duct tape on his tile floor. His friends wanted the line to be longer. Jake laid down 2/3 yards more duct tape. How long is the line of duct tape now?