Question

The ratio between the diameters of two circles is $3:5,$ then find the ratio between their circumference.

• A. $3:25$
• B. $3:5$
• C. $7:25$
• D. $19:25$

Answer 1

The correct option is B $3:5$

We know, diameter = 2 $\times$ radius.

Then, radius $=\frac{\text{diameter}}{2}$.

Given, ratio of diameter $=3:5$.

Then, ratio of radii $=\frac{3}{2}:\frac{5}{2}=3:5$.

Thus, ratio of diameter = ratio of radii.

$\therefore$ ratio of radius $=3:5$.

Now, circumference of a circle =$2\pi r$.

$\therefore$ ratio of the circumference $=2\pi \left(3\right):2\pi \left(5\right)$ $=3:5$.

Hence, option $B$ is correct.