Area by Decomposition
Find a region’s area by cutting it into rectangles and triangles (or relating shared and overlapping sub-regions) and adding or subtracting their areas; choose the base–height pair that makes each piece computable.
grade 5–6 Measurement & dataGeometry visualsubproblem
Progression (8)
g6 1. Triangle height depends on chosen base Geometry
g6 2. Use shared base to find composite area GeometryMeasurement & data
g4 3. Equal overlap area yields a segment length Measurement & data
g6 4. Solve known areas first, step by step GeometryMeasurement & data
g5 5. Decompose composite figures into rectangles Base-ten numbersMeasurement & data
g6 6. Count how many unit shapes make the whole GeometryFractions
g6 7. One ■-th of the whole is the whole divided by ■ GeometryNumber system
g7 8. Slide pieces so the shaded part becomes one lump Geometry