Definition
Composite shape
A composite shape is treated as simpler shapes joined together for measurement or reasoning.
What it means
When a shape looks complicated, split it into pieces you already know, such as rectangles or triangles. You can add the pieces, or start with a larger shape and subtract a missing piece.
Remember it
Break the big shape into familiar pieces.
Example
An L-shaped region fits inside an 8-by-6 rectangle with a 3-by-2 corner missing. Its area is 8 × 6 − 3 × 2 = 42 square units.
Watch for
A line drawn inside a shape does not automatically become an outside edge; internal seams are not counted in the perimeter.
Common mix-up
In number work, composite describes a number with extra factors; here it describes a figure made from simpler parts.
Exact meaning
A composite shape, or composite figure, is a 2D or 3D figure considered as the union of two or more simpler figures, usually so a property can be found by decomposing it. Shared internal boundaries are not part of its outside perimeter.