The formula for the area of a circle is the following:
[tex]A = \pi r^{2}[/tex]
where [tex]A[/tex] is the area and [tex]r[/tex] is the radius of the circle. We also know that the diameter of a circle is twice the length of the radius, so you are able to determine the radius using the above formula, and then you can double it to get the diameter.
