Question

A circle has an area of M cm^2 and a circumference of N cm. If M/N=20, what is the radius of the circle in cm?

Answer 1

`color(blue)(r = 40cm`

Explanation:

The formula for the area of a circle is `color(blue)(pir^2`
The formula for the circumference of a circle is `color(blue)(2pir`

The area given is : `M cm^2`

The circumference given is `N cm`

`M/N =color(blue)( (pir^2)/(2pir)) = 20`

`color(blue)( (cancelpir^2)/(2cancelpir)) = 20`

`r/2 = 20`

`color(blue)(r = 40cm`