Congruence in triangles – SSS Rule

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Investigating the possibility of congruence if three sides of two triangles are congruent.


Compare sides in triangles to check for congruence

Estimated Time

30 minutes

Prerequisites/Instructions, prior preparations, if any

Prior knowledge of point, lines, angles, closed figures

Materials/ Resources needed

  1. Digital : Computer, geogebra application, projector.
  2. Non digital : Worksheet and pencil, triangles of same and different shapes
  3. 3. Geogebra files : “SSS congruence.ggb

Download this geogebra file from this link.

Process (How to do the activity)

Prior hands on activity

  • Three triangles are distributed to groups of students.
  • Children should identify the triangles that are congruent.
  • They can name the vertices in the given triangles.
  • Write down the sides and angles that are coinciding in the two triangles.

Use the geogebra file

  • How many triangles you observe?
  • Are all the triangles same, point out the triangles that are same.
  • How can you say they are same? What can you do to check if the two triangles are congruent?
  • What parameters of triangles are required to know if they are congruent?
  • What about the third triangle is it the same as the other two, what you should do to show the triangle is same as the others – concept pf reflection can be discussed


  • Make two triangles of same sizes. Cut it and verify they are congruent.
  • Construct one triangle – Base = 3, 4 and 5 are other sides. Another triangle base = 5; and two sides are 3 and 4. Another triangle base = 4; and two sides are 3 and 5. Does the order of sides matter in a triangle?

Evaluation at the end of the activity

  • Students should be able to understand, if 3 corresponding sides of two triangles are same then the triangles are congruent.
  • Students should also understand that the sequence of sides examined in the triangles need not be same for the triangles to be congruent.