Question

the ratio of radii of a the two circles is 1:3. find the ratio of their areas .

Answer 1

let the radii be x and 3x

ratio=
$\frac{\pi {r}^{2} }{\pi {r}^{2} } \\ \\ \frac{ {x}^{2} }{ {3x}^{2} }$
your answer is 1:3.....

Answer 2

A1/A2=π×1x×1x/π×3x×3x
=1/9=1:9