Question

Find the following ratio.
The ratio of circumference of circle with radius $r$ to its area.

Answer 1

Radius of the circle = $r$ units.

Circumference of the circle = $2\pi r$ units

Area of the circle = $\pi r^2$ square units.

Circumference of the circle : Area of the circle

= $2\pi r:\pi r^2=\frac{2\pi r}{\pi r^2}=\frac{2}{r}=2:r$

Thus, the ratio of circumference of circle with radius $r$ to its area is $2:r$