Question

what is the surface area of a sphere with a radius of 9 units?
a. 576π units²
b. 648π units²
c. 288π units²
d. 324π units²

Explanation:

Step1: Recall surface - area formula

The formula for the surface area of a sphere is $A = 4\pi r^{2}$, where $r$ is the radius of the sphere.

Step2: Substitute the given radius

Given $r = 9$ units. Substitute $r = 9$ into the formula: $A=4\pi\times(9)^{2}$.

Step3: Calculate the result

First, $(9)^{2}=81$. Then $4\pi\times81 = 324\pi$ square units.

Answer:

D. $324\pi$ units$^{2}$