Lesson plan

Find scale factor by comparing dilated figures with their images

teaches Common Core State Standards CCSS.Math.Content.8.G.A.3 http://corestandards.org/Math/Content/8/G/A/3
teaches Common Core State Standards CCSS.Math.Content.8.G.A.4 http://corestandards.org/Math/Content/8/G/A/4

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Big Ideas: Understand that objects in space can be transformed in an infinite number of ways, and those transformations can be described and analyzed mathematically. The scale factor of a dilation can be found by looking at the ratio of the corresponding coordinates of the image to the preimage. If the ratios are not the same, the figure is not a dilation. This lesson builds on students' knowledge of dilations and scale factor. In this task, students are given a scenario where they are designing a playground. They are given figures and their images on a coordinate grid and they will need to use their knowledge of dilations and ratios to determine whether the transformation was a dilation, and if so, determine the scale factor. Students will need to understand that they must find the ratio of the coordinates of the image to the preimage in order to find the scale factor and that if the ratios are not equal, then the transformation was not a dilation. This builds towards the understanding the dilations result in similar figures. Vocabulary: Dilation, Scale Factor, Image, Preimage, Similar