To determine the volume of a sphere, we use the formula 4/3πr^3. So, to find the volume of a hollow sphere, we must subtract the volume of the hollow region from the volume of the overall sphere. Let’s call the radius of the overall sphere r1 and the radius of the hollowed region r2. Thus, we get 4/3π*r1^3 – 4/3π*r2^3.