Respuesta :

[tex]\bf \textit{area of a circle}\\\\ A=\pi r^2\quad \begin{cases} r=radius\\ ------\\\ A=78.5 \end{cases}\implies 78.5=\pi r^2\implies \cfrac{78.5}{\pi }=r^2 \\\\\\ \sqrt{\cfrac{78.5}{\pi }}=r[/tex]
The radius will be = 5