Education Technology

Corresponding Parts of Similar Triangles

Activity Overview

Change the scale factor (r) between similar triangles; identify the corresponding parts and establish relationships between them.


  • Students will identify corresponding parts of similar triangles.
  • Students will use the ratio of similarity to find missing measures in similar triangles.
  • Students will relate the ratio of similarity to reductions and enlargements.


  • scale factor (ratio of similarity)
  • corresponding parts
  • reduction
  • enlargement
  • coincide; coincidental

About the Lesson

This lesson involves manipulating the scale factor (r) and observing changes in similar triangles; changing the ratio of similarity; and matching corresponding parts of similar triangles. As a result students will:

  • Produce reductions, enlargements, and congruent figures.
  • Compare corresponding angles and corresponding sides to be compared.
  • Infer the relationship between ratio of similarity (scale factor) and the measures of the sides.