Question

If the ratio of the circumference of two circles is $3:1$, then find the ratio of their areas.

Answer 1

Circumference of a circle $=2\pi r$

Ratio $=3:1$

Lets consider radius to be $r_1$ and $r_2$

$r_2=3r_1$

Area $=\pi r^2$

Therefore ratio of areas $=r_2^2:r_1^2=3^2{r}_1^2:r_1^2$

$=9:1$