A full circle can be thought of as a sector of a circle with 360° of central angle. For a sector of a circle with a central angle of n°, multiply the area of the circle by the fraction n°/360°.
The formula for the area of a sector of circle with central angle n° and radius r is
Since the area of a circle is pi r^2, we basically have to replace the r with 40, since it's the radius. Therefore when replaced, it would be pi(40)^2. This makes 1600pi. Pi is technically 3.14, so I multiplied 3.14 and 1600 to get 5,024 inches squared.
