Math6-8
Triangle Congruence: SSS, SAS, and SSA
By Keith F.
A multi-day geometry practice set for 8th graders that teaches the triangle congruence theorems SSS and SAS, scaffolds in ASA and AAS, and shows why SSA does not guarantee congruence. Students color-match corresponding parts across paired triangles to build visual reasoning and precise use of the theorem names.
Customize for your classroom
Teacher Guide & Tips
- Use Day 1 as a 45-minute block: review the key terms, walk through the SSS and SAS reference table together, then have students color-match the pairs independently or in pairs.
- Discussion question: Why does the order of letters in SAS matter, and why does SSA fail when the angle is not included between the two sides?
- Scaffold for struggling readers: provide a labeled sample pair with the included angle and included side already highlighted before students attempt the matching.
- Extension for advanced students: ask them to construct a counterexample for SSA by drawing two non-congruent triangles that share two sides and a non-included angle.
- Estimated time: about 45 minutes per day, plus a short wrap-up discussion of the SSA counterexample.
Math6-8
Triangle Congruence: SSS, SAS, and SSA
By Keith F.
A multi-day geometry practice set for 8th graders that teaches the triangle congruence theorems SSS and SAS, scaffolds in ASA and AAS, and shows why SSA does not guarantee congruence. Students color-match corresponding parts across paired triangles to build visual reasoning and precise use of the theorem names.
Customize for your classroom
Teacher Guide & Tips
- Use Day 1 as a 45-minute block: review the key terms, walk through the SSS and SAS reference table together, then have students color-match the pairs independently or in pairs.
- Discussion question: Why does the order of letters in SAS matter, and why does SSA fail when the angle is not included between the two sides?
- Scaffold for struggling readers: provide a labeled sample pair with the included angle and included side already highlighted before students attempt the matching.
- Extension for advanced students: ask them to construct a counterexample for SSA by drawing two non-congruent triangles that share two sides and a non-included angle.
- Estimated time: about 45 minutes per day, plus a short wrap-up discussion of the SSA counterexample.