Question

The area of a circle is 81pie square feet. What is the length of the radius? What is the length of the diameter? Please show steps!

Answer 1

`</p><p>A=81\pi \\</p><p>A=\pi r^2 \\</p><p>81\pi=\pi r^2\Longrightarrow r^2=81</p><p>radius=√(81)=\boxed{9} \\</p><p>diameter=2radius = 2\cdot9=\boxed{18}</p><p>`

Answer 2

`\bf \textit{area of a circle}\\\\ A=\pi r^2~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ A=81\pi \end{cases}\implies 81\pi =\pi r^2\implies \cfrac{81\pi }{\pi }=r^2\implies 81=r^2 \\\\\\ √(81)=r\implies \boxed{9=r}~\hspace{10em}\stackrel{\textit{diameter = twice the radius}}{18}`