Answers:
- Lateral Area = 108 square km
- Surface Area = 120 square km
===============================================
Explanation:
Think of the triangles as the floor and ceiling of this 3D room. The walls are the three rectangular sides.
We have a 9 by 4 wall with area 9*4 = 36 square km
We have a 9 by 3 wall with area 9*3 = 27 square km
We have a 9 by 5 wall with area 9*5 = 45 square km
The lateral area is 36+27+45 = 108
-----------------
The two triangles form the base faces of this prism.
Let's find the area of one of the triangles
area = 0.5*base*height = 0.5*3*4 = 6
One triangle has area 6, so both triangles in total have area 2*6 = 12 square km.
The total surface area is therefore 108+12 = 120 square km
