The formula of circumference for a circle is ((or 3.14){pie})*(d(or 2 radius))
The formula for area for a circle is {pie}*r^2
That way.............
9*2=18*3.14(shortcut for pie)= 56.52
So out circumference would be 56.52km^2
Area
9^2=81*3.14=254.34
So our area would be 254.34 km^2