Question

What is the radius of this problem ?

Answer 1

$\bf \textit{area of a circle}\\\\ A=\pi r^2\qquad \begin{cases} r=radius\\ ------\\ A=64\pi \end{cases}\implies 64\pi =\pi r^2 \\\\\\ \cfrac{64\pi }{\pi }=r^2\implies 64=r^2\implies \sqrt{64}=r\implies 8=r$

Answer 2

$A= \pi r^2 \\ \\ \pi r^2=64 \pi \ \ \to \ \ r^2= \frac{64 \pi }{ \pi } \ \ \to \ \ r= \sqrt{ 64 } = 8$