The circle expands it radius 20m each day. From this description you can get this equation:
r=0+ 20*d
r=20d
The oil slick expands as a circle and the formula for circle area is
r^2. If you insert the first equation into this equation you will got:
circle area = r^2
circle area = (20d)^2
circle area = 400*d^2
r=0+ 20*d
r=20d
The oil slick expands as a circle and the formula for circle area is
circle area =
circle area =
circle area =