Question

If the ratio of circumference of two circles is 5:7, then the ratio of its diameters is _____

• A. 7:5
• B. 5:7
• C. 25:49
• D. 10:49

Answer 1

The correct option is B 5:7

Circumference of a circle = $2\pi$r
= $\pi$d [$\because$ d=2r]
Ratio of circumference of a circle = 5:7

$\Rightarrow \frac{\text{circumference of circle 1}}{\text{circumference of acircle 2}}=\frac{5}{7}$

$\Rightarrow \frac{\pi d1}{\pi d2}=\frac{5}{7}$

$\Rightarrow \frac{d1}{d2}=\frac{5}{7}$