Question

If the ratio of the areas of the two circle is $4:9$, then the ratio of their circumferences is

• A. $9:4$
• B. $2:3$
• C. $4:9$
• D. $16:81$

Answer 1

The correct option is B $2:3$

$\frac{(A{)}_1}{(A{)}_2}=\frac{4}{9}\Rightarrow \frac{\pi r_1^2}{\pi r_2^2}=\frac{4}{9}\Rightarrow \frac{r_1}{r_2}=\frac{2}{3}$

$\frac{C_1}{C_2}=\frac{2\pi r_1}{2\pi r_2}=\frac{r_1}{r_2}=\frac{2}{3}$