The pool at a park is circular. You want to find the equation of the circle that is the boundary of the pool. Find the equation if the area of the pool is 400 square feet and (0, 0) represents the center of the pool.
A.x2 + y2 = 20
B.x2 + y2 = 400
C.x2 + y2 = 400 pi
D.x2 + y2 = 400/pi

Question

The pool at a park is circular. You want to find the equation of the circle that is the boundary of the pool. Find the equation if the area of the pool is 400 square feet and (0, 0) represents the center of the pool. 
 A.x2 + y2 = 20  
 B.x2 + y2 = 400  
 C.x2 + y2 = 400 pi  
 D.x2 + y2 = 400/pi

btaylor · Answer

in the formula for the graph of a circle
(x-h)^2 - (y-k)^2 = r^2
we need r^2. So to find that, we divide the area by π. So D. is the right answer.