Education Technology

Similar Figures

Activity Overview

Observe what happens to ratios of pairs of side of rectangles and triangles.


  • Students will identify corresponding sides and corresponding angles.
  • Students will understand and use the definition of similar figures.


  • ratios
  • corresponding sides
  • corresponding angles
  • congruent
  • similar figures

About the Lesson

Drag vertices of rectangles and triangles and observe what happens to ratios of pairs of sides within each figure. As a result, students will:

  • Apply the definition of similarity to identify similar figures.
  • Make connections between ratios within figures to ratios between figures.
  • Confront two common misconceptions: defining similar figures as those with the same shape but different size and identifying all rectangles as similar.