Question

question 3 of 10
what is the surface area of a sphere with a radius of 9 units?
a. $576\pi$ units$^2$
b. $648\pi$ units$^2$
c. $288\pi$ units$^2$
d. $324\pi$ units$^2$

Explanation:

Step1: Recall sphere surface area formula

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

Step2: Substitute radius $r=9$

Substitute $r=9$ into the formula:
$SA = 4\pi (9)^2$

Step3: Calculate $9^2$ first

$9^2 = 81$, so:
$SA = 4\pi \times 81$

Step4: Compute the product

$4 \times 81 = 324$, so:
$SA = 324\pi$

Answer:

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