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Similarity and Proportion

Similarity is more than "same shape, different size." In this unit, students develop a more formal definition of similarity in lessons emphasizing that similar figures have congruent corresponding angles and proportional corresponding sides. They identify the corresponding parts of similar triangles, discover minimal requirements to guarantee similarity, investigate special cases such as nested triangles, and explore the relationships for area and perimeter of similar figures.

Geometry: Similarity and Proportion Activities

Title Type

Similar Figures

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

Alignments  Standards  |  Textbook  
  • 6934

Corresponding Parts of Similar Triangles

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

Alignments  Standards  |  Textbook  
  • 6662

Angles and Similarity

Experiment with the measures of the angles of similar triangles to determine conditions necessary for two triangles to be similar.

Alignments  Standards  |  Textbook  
  • 6834

Nested Similar Triangles

Discover the conditions that make triangles similar by moving the sides opposite the common angle in nested triangles.

Alignments  Standards  |  Textbook  
  • 6363

Triangle Midsegments

Investigate the relationships between a triangle and the similar triangle formed by one of the triangle's midsegments.

Alignments  Standards  |  Textbook  
  • 6373

Scale Factor Area Perimeter

Explore the relationship of perimeter and area in similar triangles when the scale factor is changed.

Alignments  Standards  |  Textbook  
  • 6455

Ratios of Similar Figures

Students explore the ratio of perimeter, area, surface area, and volume of similar figures in two and three dimensional figures.

Alignments  Standards  |  Textbook  
  • 4740
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