Answer:
Total surface area = 27 km²
Explanation:
The surface area of a square based pyramid comprises:
- 4 congruent triangles (sides)
- 1 square (base)
Area of a triangle = 1/2 × base × height
= 1/2 × 3 × 3
= 4.5 km²
Area of a square = (side length)²
= 3²
= 9 km²
Total surface area = 4 triangles + square base
= (4 × 4.5) + 9
= 18 + 9
= 27 km²