## Introductory Algebra for College Students (7th Edition)

$r=\sqrt{\frac{A}{\pi}}$
To solve for r, isolate r on one side of the equation. $A=\pi r^2$ Divide both sides by $\pi$. $\frac{A}{\pi}=\frac{\pi r^2}{\pi}$ Simplify. $\frac{A}{\pi}=r^2$ Take the square root of each side. $\sqrt{\frac{A}{\pi}}=\sqrt{r^2}$ Simplify. $\sqrt{\frac{A}{\pi}}=r$