We want to find the diameter of a circle which has an area = 209.
The formula to find area of a circle is:

Where
A is the area
r is the radius
Let's find the radius, first by putting in value of Area and doing some algebra. Shown below:
![\begin{gathered} A=\pi r^2 \\ 209=\pi r^2 \\ r^2=(209)/(\pi) \\ r=\sqrt[]{(209)/(\pi)} \\ r=8.156 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/2ltsvqoiev8yrgz5a4i8xsdn6o0n5n9t6n.png)
THis is the radius.
We know
diameter is TWICE the radius, so
diameter = 2 * 8.156
diameter = 16.312
Rounding to nearest tenth (1 decimal place), we have
Diameter = 16.3 meters