[tex]\begin{gathered} r\colon\text{ radius} \\ d\colon\text{ diameter} \\ \\ \text{ the radius is half of the diameter.} \\ r=\frac{18}{2} \\ \\ r=9\text{ feet} \end{gathered}[/tex][tex]\text{ the diameter is 18 feets}[/tex][tex]\begin{gathered} C\colon\text{ circumfence} \\ C=2\pi r \\ C=2\pi\cdot9 \\ C=18\pi\text{ feet} \end{gathered}[/tex][tex]\begin{gathered} A\colon\text{ area} \\ A=r^2\pi \\ A=9^2\pi \\ A=81\pi\text{ feet} \end{gathered}[/tex]
