Volume of large sphere is 4/3(pi)r^3 where r is the radius, and the volume of the smaller sphere is 4/3(pi)(r/4)^3 where the radius is a quarter that of the large sphere, because the diameter of the small sphere is 7cm, so its radius is 3.5cm, a quarter of 14cm. Dividing the volume of the small sphere into that of the larger sphere gives us 4^3=64. So since all of the large sphere is used to make the smaller spheres, 64 smaller spheres can be made.