Question

A circle has an area of 80 square centimeters. Which answer is closer to the measure of its radius?

Answer 1

Since the area of a circle is
`S=\pi r^2`
`\Rightarrow`
`80=\pi r^2`.

Now we are going to divide each side by
`\pi`.


`(80)/(\pi)=r^2 \\r=\pm\sqrt{(80)/(\pi)} \\r=\pm(√(80))/(√(\pi))\approx\pm5.05 \ cm`

Since the radius could not be negative
`\Rightarrow` your answer is positive
`5.05 \ cm`.