Geometry
Confusing Similar and Congruent Figures
Students treat figures with the same shape as if they must have the same size.
Quick check
Why students make it
The words similar and congruent both sound like the figures match. This can make students ignore whether the scale factor is or a different number.
The rule done right
Similar figures have the same shape, so corresponding angles are equal and corresponding side lengths are proportional. Congruent figures have the same shape and the same size, so corresponding angles and corresponding side lengths are equal.
Related resources
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Geometry, Proving Triangle Similarity Infographic -
Scale Factor & Similar Figures Infographic -
Geometry, Triangle Congruence Postulates Infographic -
What CPCTC Means in Geometry Infographic -
Geometry, Corresponding Angles Infographic - Similarity & Congruence Reference Cheat Sheet
- Similarity & Congruence Cheat Sheet
- Similar Triangles and Scale Factor Worked Examples Cheat Sheet
- Triangle Inequality and Side Angle Relationships Cheat Sheet
- Angles & Angle Relationships Cheat Sheet
- Math, Similar and Congruent Figures Worksheet
- Geometry, Triangles Worksheet
- Geometry, Angles Worksheet
- Ratios & Proportions Worksheet
- Geometric Transformations Visualizer Tool
- Ratio & Proportion Visualizer Tool
- Angle Relationships Explorer Tool
- Similarity & Triangle Trigonometry Lab Lab
- Congruence & Transformations Lab Lab
- Angle Relationships Lab Lab
- Geometric Constructions Lab Lab