The area of an equilateral triangle is $9\sqrt{3}{\text{cm}}^2$, find its perimeter.

The formula for the area of an equilateral triangle is:
$$\text{Area}=\frac{\sqrt{3}}{4}{a}^2$$
where $a$ is the side length of the triangle.Given:
$$\frac{\sqrt{3}}{4}{a}^2=9\sqrt{3}$$
$$a^2=9\times 4=36$$
$$a=6\text{cm}$$
The perimeter of an equilateral triangle is given by:
$$\text{Perimeter}=3a=3\times 6=18\text{cm}$$