CBSE Lesson

Geometric Twins: Discovering Congruence

Shared by A STEM Educator★ Featured Teacher · rated 90+ in our quality review

7th Grade5E Model740 min

Learning Objective

Students will identify congruent figures, apply congruence criteria (SSS, SAS, ASA) to triangles, and use congruence to find unknown sides and angles.

Lesson Overview

Students explore the concept of congruence in triangles and other figures, discovering the conditions (SSS, SAS, ASA) under which two shapes are identical in size and shape. Activities are discussion-based and pencil-and-paper throughout.

Materials

Paper
Pencil
Whiteboard and markers

Scaffolded Task Progression

1Task 1

Look at the two triangles below. Without any measurements, can you say they are congruent? What is the minimum information you would need to be sure?

[ Interactive graph / diagram, available in the full lesson ]

[ Interactive graph / diagram, available in the full lesson ]

Write two things you would measure to start checking.

2Task 2

Part A — SSS Test. You and your partner both draw a triangle with sides

6

cm,

4

cm, and

5

cm (in any order you like). Trace one and place it on the other.
(a) Do they match exactly?(b) Could you have made a different triangle with those three sides? Part B — Two sides only. Now both draw a triangle with only two sides given:

6

cm and

4

cm (no angle told). Compare.(c) Did you both get the same triangle? Why or why not?

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