Explanation
The formula to calculate the area of a circle is:
[tex]\begin{gathered} A=\pi r^2 \\ \text{ Where} \\ A\text{ is the area} \\ r\text{ is the radius} \end{gathered}[/tex]
So, we have:
[tex]r=\frac{\text{ diameter}}{2}=\frac{18cm}{2}=9cm[/tex][tex]\begin{gathered} A=\pi r^{2} \\ A=\pi(9cm)^2 \\ A=81\pi cm^2 \end{gathered}[/tex]Answer
81π cm²
