[tex]\stackrel{\textit{area of the great circle}}{A=\pi r^2}\hspace{5em}81\pi =\pi r^2\implies \cfrac{81\pi }{\pi }=r^2\implies 81=r^2 \\\\\\ \sqrt{81}=r\implies 9=r \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{surface area of the sphere}}{SA=4\pi r^2}\hspace{5em}SA=4\pi (9)^2\implies SA=324\pi ~in^2[/tex]
