Grade 7 · Spatial Sense · Three-Dimensional Geometry
Classify Three-Dimensional Objects
Three-dimensional objects belong to classes because of properties that stay true even when the object is turned or stretched.
The big idea
Defining properties rule out whole classes
A prism has two parallel congruent polygon bases. A pyramid has one polygon base and triangular faces that meet at one vertex.
Work it through
Classify an object with two congruent triangular bases
- 1. Identify two congruent, parallel bases.
- 2. Name the base shape: triangle.
- 3. Check that connecting faces are parallelograms.
- 4. Classify the object as a triangular prism and then examine its planes of symmetry.