the base edge of a triangular pyramid is 3 meters and its altitude is 10 meters. Find the area of asection parallel to the base and 6 meters from it.

Solution:

The section parallel to the base is also an equilateral triangle.

The edge/ base edge = (10-6)/10 = 2/5

the edge = 2/5 * base edge = 3*2/5 = 1.2 meters

The area = sqrt(3)/4 * 1.2^2 = 0.624 square meters