Focus: Work in this unit extends students’ skills with transformations of plane figures and their knowledge of geometry and geometric measurement. This unit draws on familiarity with representations and formulas for the area of rectangles, parallelograms, and triangles, and students’ abilities to use rulers and protractors. This unit specifically builds on early skills developed in CKMath Grade 7 Unit 1 Scale Drawings. Students learn to describe pairs of scaled copies in terms of specific rotations and transformations and are introduced to the concepts of scale factor and similarity.
Students use the definition of similarity to analyze the properties of triangles and determine if they are similar or non-similar. They then apply this knowledge of similar triangles to an introduction to slope (i.e., similar triangles on the same line). Throughout this unit, students discuss their mathematical ideas and respond to the ideas of others. In the following unit, Grade 8 Unit 3: Linear Relationships, students will extend learning from this unit to further explore representations of lines as equations as well as proportional relationships.
Number of Lessons: 13
Lesson Time: Approximately 45 minutes. Please note that each lesson is designed for one instructional block, and may be divided into shorter segments based on teacher pacing and student needs.
Additional Search Terms:
scale factor • scale copy • scaling • dilation • center of dilation • dilate • similar • quotient • unit • slope • slope triangle • similarity • x-coordinate • y-coordinate • equation • line • grid • estimate • approximate • mathematical practices