1. The problem statement, all variables and given/known data Three identical balls fit snugly into a cylindrical can: the radius of spheres equals the radius of can, and the balls just touch the bottom and the top of the can, If the formula for the volume of a sphere is V = 4/3 PI * radius * radius * radius, what fraction of the volume of the can is taken up by the balls? 2. Relevant equations Volume of sphere = 4/3 PI * r * r * r Volume of cylinder = PI * r * r * h 3. The attempt at a solution Suppose diameter of each ball is 2 so r = 1. Vol of 3 balls = 3 * 4/3 PI * r * r *r = 4 * PI Volume of cylinder = PI * r * r * h Note h = 6 because 3 balls can fit in the cylinder Volume of cylinder = 6 * PI volume take up by balls is= 6* PI - 4 * PI = 2 PI book is not doing subtraction., Some body please guide me why are we not doing subtraction. Zulfi.