Question

Find the area of an equilateral triangle with height 9 m

Answer 1

area
$= \frac{1}{2} \times b \times h$
$\frac{1}{2 } \times 9 \times 9 = \frac{81}{2} = 40.5m^{2}$

Answer 2

Altitude drawn on side of equilateral triangle bisects it.
Further refer the image
Also sorry for my handwriting
Shortcut method
Area of equilateral triangle
=√3/4*a^2
or
=h^2/√3
which could be observed in the given case

Hope it helps