[tex]\bf \textit{area of a circle}\\\\
A=\pi r^2\quad
\begin{cases}
r=radius\\
-----\\
r=\stackrel{r\times 3}{3r}
\end{cases}\implies A=\pi (3r)^2
\\\\\\
A=\pi (3^2r^2)\implies A=9(\pi r^2)[/tex]
notice, if the original area was πr², then the new area has a factor in front of it, that much.
