Find diameter (another 10th grade Geometry question)?

Question

I'm stuck on this question..please help if you can..here it is:

A circle has area 225 pie M squared. What is the diameter of the circle?

Answer 1

I'm guessing M is a variable? So here is the equation worked out:

225πM² = πr²

Divide both sides by π

225M² = r²

Then find the square root of 225M² which is 15M. 15M x 15M = 225M².

Now you know that r = 15M

Diameter is 2 times the radius.

So your diameter is 30M