Question

Finally, you make an approximately circular yard using 80 ft of fence. What is the area of the yard? (Hint: First find the radius of the yard.)

Answer 1

Since the circumference is 80, you know that the equation used was:
$\pi d = 80$
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 $\pi r^2$
So, $\pi (12.723)^2$ = 508.544 square feet