Since the circumference is 80, you know that the equation used was:
[tex] \pi d = 80[/tex]
Divide by pi and you'd get d = 25.465
Divide that by 2 to get your radius.
25.465 / 2 = 12.723 = r
The area formula for a circle is [tex] \pi r^2[/tex]
So, [tex] \pi (12.723)^2[/tex] = 508.544 square feet
