## Geometry: Common Core (15th Edition)

Use the formula for the area of a circle. $A=\pi r^2$ substitute $10\pi=\pi r^2$ divide each side by $\pi$ $10\pi\div\pi=\pi r^2\div\pi$ $10=r^2$ take the square root of each side $\sqrt{10}=\sqrt{r^2}$ $3.16=r$ The diameter is twice the radius. $d=2r=2(3.16)=6.32$