Question

How does the surface area of a sphere change when the radius is tripled?A. The surface area doesn't changeB. The surface area is increased by 9C. The surface area is doubledD. The surface area is multiplied by 9

Answer 1

We must have in mind the surface of a sphere that is given by

$S_a=4\pi r^2$

When the radius of the sphere triples, the new radius becomes r1=3r. So, the new surface area of a sphere is

$S_{a1}=4\pi(3r)^2=9(4\pi r^2)=36\pi r^2$

As we can see, the surface area is multiplied by 9. The correct answer is D.