I would like if I have done this correct and I also need help with one thing in this problem.

What is the area of a circle w/circumference 18pi centimeters? Give your answer in terms of pi.

My answer so far is: C= 2pi r --> 18pi = 2pi r --> 18pi/2pi = 2pi r/2pi --> 9= r

A= pi r^2 --> A= pi (9)^2 --> A= 81pi --> A= 254.4690049 centimeters

Now what I'm confused in is how do I write my answer in pi terms? I have look in my book and I have no luck.

Thank you for the help.