Question

The circumferences of two circles are in the ratio $5:7$, find the ratio between their radii.

• A. $\frac{5}{7}$
• B. $\frac{5}{6}$
• C. $\frac{2}{5}$
• D. $\frac{3}{5}$

Answer 1

The correct option is A $\frac{5}{7}$

Given $C_1:C_2=5:7$

$C_1:C_2=2\pi R_1:2\pi R_2$

$5:7=R_1:R_2\Rightarrow R_1:R_2=5:7$