Question

The circumferences of two circles are 3 m. and 9p m. What is the ratio of the areas of the circle?

Answer 1

Circumferences: $C_1=2\pi r_1,\;C_2=2\pi r_2.$

$\frac{r_2}{r_1}=\frac{C_2}{C_1}=\frac{9}{3}=3.$

Areas: $A_1=\pi r_1^2,\;A_2=\pi r_2^2.$

$\frac{A_2}{A_1}=\frac{r_2^2}{r_1^2}=3^2=9.$