Question

A circle has an area of 8080 square centimeters. Which answer is closest to the measure of its radius?

Answer 1

The formula for area of a circle is pir^2, simply reverse it to get your answer.
The answer should be 28.613.  Also, you forgot to add the choices.  it is hard to answer your questions if you don't give all the information.

Answer 2

The area of a circle is $\pi r^2$. Thus, $8080 = \pi r^2$. Now divide $8080$ by $\pi$ to get your answer of $24.5$.
This should be the correct answer.