The area of an equilateral triangle is cm². Its height is-

It is given in the question that,

Area of an equilateral triangle = 81 cm²

Let a be the side of the triangle and h be the height

We know that,

Area of an equilateral triangle =

81 =

a² = 81 × 4

a = 18

Also, Area of triangle =

81

h =

h = 9 cm

Hence, option (a) is correct