The altitude of an equilateral triangle having perimeter 18 m, is

Perimeter of a equilateral triangle = 18m

then the side = \(\frac{18}{3}\) = 6m

Altitude of the triangle = \(\frac{\sqrt {3}}{2}\) × (side)

= \(\frac{\sqrt {3}}{2}\) × (6) = $3\sqrt{3}$ m