Area of square base = 324 m²
Length of the square side = √324 = 18
The side of the square is the base of the triangle.
Area of triangle = (1/2)*base* height
135 = (1/2)*18* h
135 = 9h
135/9 = h
15 = h
height = 15 m
To get the height of the Pyramid, the height of the Triangle and half the length of the side of the square form a right angled triangle.
Hypotenus = 15
Half length of square = 18/2 = 9
Height of Pyramid = H
By Pythagoras' Theorem:
15² = H² + 9²
225 =H² + 81
H² + 81 = 225
H² = 225 - 81
H² = 144 Take square root of both sides
H = √144
H = 12
Height = 12 meters.
Option C.