Question

The radius of a large sphere is 8 times the radius of a small sphere. the surface area of the large sphere is how many times the surface area of the small sphere?

Answer 1

Large sphere's radius = R,
small sphere's radius = r, R = 8r
surface area of a sphere (SA) = 4×pi×radius^2
So what we need is the SA of the larger in terms of the smaller sphere, so if:
SA (of R) = 4×pi×R^2, then plug in "8r" for "R"...
SA = 4×pi×(8r)^2 = 4×3.14×64r^2
SA = 12.57×64r^2 = 804 r^2
Therefore the SA of the larger sphere is 804 times the SA of the smaller sphere.
I hope that makes sense!