The purpose of this lesson is to draw and interpret scale diagrams that represent enlargements.

Included is a YouTube video to support Grade 9 Blended Learning Math - Unit 7.1: Similarity and Transformations - Scale Diagrams and Enlargements.

The purpose of this lesson is to recognize and draw similar polygons, then use their properties to solve problems.

Included is a YouTube video to support Grade 9 Blended Learning Math - Unit 7.3: Similarity and Transformations - Similar Polygons.

The purpose of this lesson is to use the properties of similar triangles to solve problems.

Included is a YouTube video to support Grade 9 Blended Learning Math - Unit 7.4: Similarity and Transformations - Similar Triangles.

Through this lesson and its two associated activities, students are introduced to the use of geometry in engineering design, and conclude by making scale models of objects of their choice. The practice of developing scale models is often used in engineering design to analyze the effectiveness of proposed design solutions. In this lesson, students complete fencing (square) and fire pit (circle) word problems on two worksheets—which involves side and radius dimensions, perimeters, circumferences and areas—guiding them to discover the relationships between the side length of a square and its area, and the radius of a circle and its area. They also think of real-world engineering applications of the geometry concepts.

Students build scale models of objects of their choice. In class they measure the original object and pick a scale, deciding either to scale it up or scale it down. Then they create the models at home. Students give two presentations along the way, one after their calculations are done, and another after the models are completed. They learn how engineers use scale models in their designs of structures, products and systems. Two student worksheets as well as rubrics for project and presentation expectations and grading are provided.