# How do you find the area of a circle with circumference 45?

I found $161$ u.a.
The circumference $C$ is given by:
$C = 45 = 2 \pi r$
so that $r = \frac{45}{2 \pi}$
The area will be: $A = \pi {r}^{2}$ and using our radius we get:
$A = \pi \left({45}^{2} / \left(4 {\pi}^{2}\right)\right) = \frac{2025}{4 \pi} = 161$ units of area