### Theory:

Now, we shall find the perimeter of an equilateral triangle.

Let $$ABC$$ be an equilateral triangle with sides of equal length $$s$$ $$units$$.

Then, the perimeter of the triangle $$ABC$$ is given by:
Perimeter of the triangle $$=$$ Product of $$3$$ sides and its side length
Perimeter $$P = AB+BC+CA$$ $$units$$

$$P = s+s+s$$ $$units$$

$$P = 3s$$ $$units$$

Therefore, the perimeter of an equilateral triangle is the product of $$3$$ sides and the side length.
Example:
1. The side length of an equilateral triangle is $$9 \ cm$$. Find the perimeter of an equilateral triangle.

Solution:

The side length of an equilateral triangle is $$s = 9$$ $$cm$$.

Perimeter $$= 3s$$, where $$s$$ is the length of three equal sides.

Substituting the value of $$s$$ in the above formula, we have:

Perimeter $$= 3 \times 9$$ $$cm$$

Perimeter $$= 27$$ $$cm$$

Therefore, the perimeter of an equilateral triangle is $$27 \ cm$$.