Question

A circle has an area of 40 square inches. Find the radius to 2 decimal places.

Answer 1

The area of a circle is given by

$A=\pi r^2$

We can solve this equation for r: divide both sides by pi:

$r^2=\dfrac{A}{\pi}$

Consider the (positive) square root of both sides:

$r = \sqrt{\dfrac{A}{\pi}}$

So, in your case, we have

$r = \sqrt{\dfrac{40}{\pi}}\approx 3.57$