What is the area of a circle with circumference of 37.68? (Use 3.14 for p.)

The area of a circle is pi * r^2

circumference is 2 * pi * r

so we have to make the other side look like what area equals:

c = 2pr

divide both sides by 2

c/2 = p * r

square both sides and get

(c^2) / 4 = p^2 * r^2

now divide both sides by pi and get

(c^2) / (4*pi) = pi * r^2

compare to area equation

pi * r^2 = a

pi * r^2 = (c^2) / (4*pi)

So

a = (c^2) / (4*pi)

So

a = (37.68^2) / (4 * 3.14)

a = 113.04