The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)^{2} : a = π r^{2}.
The formula for the area of a circle is which of the following?
c = π d^{2} 

c = π r^{2} 

c = π d 

c = π r 