Respuesta :

Medunno13

Answer:

[tex]r=\frac{\sqrt{314\pi}}{2\pi}[/tex]

Step-by-step explanation:

[tex]A=\pi r^2 \\ \\ 78.5=\pi r^2 \\ \\ r^2=\frac{78.5}{\pi} \\ \\ r=\frac{\sqrt{314\pi}}}2\pi}[/tex]