Use $\displaystyle{r}={10}\usepackage{cmbright}\Huge\$ in the formula $\displaystyle{A}=\pi{{r}}^{{2}}\usepackage{cmbright}\Huge\$ to find the area:

$\displaystyle{A}=\pi{{\left({10}\right)}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{A}=\pi\cdot{100}\usepackage{cmbright}\Huge\$

$\displaystyle{A}\approx{3.14}\cdot{100}={314}\usepackage{cmbright}\Huge\$

Rounded to the nearest square inch, the area of one side of the flying disc is 314 square inches.