Grade 6 Math: Area of Composite Figures

Grade 6 focus: A composite figure (or compound shape) is made from simpler figures—often rectangles and triangles. You find total area by adding areas of non-overlapping parts, or by subtracting a “cut-out” from a larger rectangle.

Video lesson: Watch this Math with Mr. J example of area for composite figures made from rectangles.

Strategy: Decompose

1. Draw dashed lines to split the shape into rectangles/triangles you recognize.
2. Label unknown lengths using properties of rectangles (opposite sides equal).
3. Compute each area, then add (or subtract for holes).

Example (add regions)

An L-shape can split into two rectangles. Add their areas.

Example (subtract)

A rectangle with a rectangular hole: area = big rectangle − hole.

Explain your reasoning

Grade-level tasks often ask you to justify decompositions. Sketch, label, and show each area calculation.

Common mistakes

• Double-counting overlapping regions.
• Missing a hidden segment length needed for a sub-figure.
• Using perimeter where area is required.