Grade 6 · Spatial Sense · Composite Area and Surface Area
Decompose Area and Build Nets
Composite area and surface area are both bookkeeping problems: break a figure into known parts, calculate each part, and combine exactly once.
The big idea
Complex shapes are made from familiar faces
A trapezoid can be split into triangles and rectangles. A rectangular prism's net shows three matching pairs of rectangular faces.
Work it through
Find the surface area of a 5 × 3 × 2 prism
- 1. Find the three different face areas: 5 × 3 = 15, 5 × 2 = 10, and 3 × 2 = 6.
- 2. Each face has a matching opposite face.
- 3. Surface area = 2(15 + 10 + 6).
- 4. Surface area = 62 square units.