A geometry problem by Ajay Sambhriya

We know that the area of a square is given by $A=x^2$ where $x$ is the side length. So

$9\pi = x^2$

$x=\sqrt{9\pi}=3\sqrt{\pi}$

If a circle is inscribed in a square, the diameter of the circle is equal to the side length of the square. The circumference of a circle is given by $c=\pi d$ where $d$ is the diameter. So

$c=\pi * 3\sqrt{\pi}\approx = \boxed{16.70}$