To determine the surface area of a sphere we use the following formula:
[tex]S=4\pi r^2,[/tex]where r is the radius of the sphere.
We are given that the radius of the sphere is 9 cm, therefore:
[tex]S=4\pi(9cm)^2.[/tex]Simplifying the above result, we get:
[tex]S=4\pi(81cm^2)=324\pi\text{ cm}^2.[/tex]