Study guide: Use Shape Attributes to Build and Describe
Distinguish defining features, build flat composites, and describe solid models.
Ideas to explain in your own words
- A geometric name depends on features such as straight sides, a closed boundary, and corners.
- Shape pieces can form a new outline when joined along matching full edges.
- A solid model can be composed of matching cubes.
- A piece can keep its own shape name while belonging to a differently named whole.
Useful vocabulary
- defining attribute
- A feature required by a shape’s definition.
- composite
- A figure built from two or more pieces.
Watch your reasoning
- Squares are also rectangles; rectangles do not have to have unequal adjacent sides.
- Shared joining edges are inside the composite, not new outside sides.
- A cube’s faces are not separate component cubes.
- A composite’s name does not automatically name each part.
A worked review example
For a triangle, three straight sides are defining. Being red is not. A large red triangle and a small blue triangle both have three straight sides forming a closed boundary. An open drawing of three disconnected lines does not make a triangle. Ask whether changing a feature would change the shape’s definition. Squares are also rectangles; rectangles do not have to have unequal adjacent sides. Make a list of required features separately from optional appearance choices.
Make a practice plan
- Separate Defining Attributes from Color: Draw two very different triangles. Expected: color, orientation, or size differ while three straight sides remain.
- Build a Rectangle from Adjacent Squares: Make a row of four squares. Expected: a rectangle four square-widths long and one high.
- Describe a Solid Made from Smaller Solids: Three layers of four cubes use 12 cubes. Draw or explain all three layers.
- Describe a Piece and the Composite Whole: Describe the pieces and whole of a rectangle split by a diagonal. Expected: two triangles; rebuilt rectangle.