Answer:
54 cm
Step-by-step explanation:
The area (A) of an equilateral triangle is
A = [tex]\frac{s^2\sqrt{3} }{4}[/tex] ( s is the side length ) then
[tex]\frac{s^2\sqrt{3} }{4}[/tex] = 81[tex]\sqrt{3}[/tex] ( multiply both sides by 4 to clear the fraction )
s²[tex]\sqrt{3}[/tex] = 324[tex]\sqrt{3}[/tex] ( divide both sides by [tex]\sqrt{3}[/tex] )
s² = 324 ( take the square root of both sides )
s = [tex]\sqrt{324}[/tex] = 18
Thus
perimeter = 3 × 18 = 54 cm
