"A large circular pane of glass has a perimeter of 219.8cm, calculate the area of the glass"?

Now it's been 25 years since I needed to use pi(stop laughing at the back).

To get the radius I need to divide the perimeter(circumference) by pi and then divide the diameter by 2, correct?

Then calculate the area by using the pi x r2(pi x radius x radius) correct?

I get an answer of- area = 3846.5.

According to my daughters friends rather stuck up school teacher mother, it's wrong.

Is it, I'd dearly love to tell her she was in fact wrong.

Sorry for boring you's but it's bugging me.