Since you are given the area, we can solve for radius with this equation:
[tex]A_c = \pi r^2[/tex]
[tex]r = \sqrt{ \frac{A_c}{ \pi } } = \sqrt{ \frac{121 \pi }{ \pi } } = \sqrt{121} = 11 [/tex]
The radius is 11, so the diameter must be 2 times that, which is 22. With the correct units, the answer is 22 units²
