# What is the area of an equilateral triangle with a perimeter of 21 inches?

Apr 22, 2018

$\frac{49 \sqrt{3}}{4}$

#### Explanation:

Let side length be $a$ inches.

Then $3 a = 21 \text{ "rArr" } a = 7$

Area of an equilateral triangle is given by

$\text{ } \frac{\sqrt{3} {a}^{2}}{4}$

$\Rightarrow \text{ } \frac{\sqrt{3} \times {7}^{2}}{4} = \frac{49 \sqrt{3}}{4}$