a circle has only one "dimension", or namely a defining component, and that's only the radius "r",
[tex]\bf \textit{area of a circle}\\\\
A=\pi r^2\qquad \boxed{A=64\pi }\qquad 64\pi =\pi r^2\implies \cfrac{64\pi }{\pi }=r^2
\\\\\\
64=r^2\implies \sqrt{64}=r\implies 8=r[/tex]
