[tex]\begin{gathered} \text{Circunference = pi}\cdot\frac{d^2}{4} \\ \text{Circunference = (3.14)}\cdot\text{ }\frac{21^2}{4} \\ \text{Circunference = (3.14) }\cdot\text{ }\frac{441}{4} \\ \text{Circunference = (3.14) }\cdot\text{ 110.25} \\ \text{Circunference = 346.19 in}^2 \end{gathered}[/tex]
The result is 346.19 in^2
