Surface Area of a Sphere = 4π(d/2)²
Let the smaller sphere's diameter be just a sample of 4 units in diameter and let the large spheres diameter be 4 times that of the smaller sphere.
Small Sphere: 4π(4/2)² = 16π units²
Large Sphere: 4π(16/2)² = 256π units²
256π / 16π = 16 times
The large sphere has a surface area 16 times that of the smaller one.
