Answer 1

Radius of the circle = r units
∴ Circumference of the circle = 2πr units
Area of the circle = πr² square units
Circumference of the circle : Area of the circle =
`2πr : πr^2 = (2πr) / (πr^2) = 2/r = 2 : r`
Thus, the ratio of circumference of circle with radius r to its area is 2 : r.