Lesson 3

Making Scaled Copies

In the previous lesson, students learned that we can use scale factors to describe the relationship between corresponding lengths in scaled figures. Here they apply this idea to draw scaled copies of simple shapes on and off a grid. They also strengthen their understanding that the relationship between scaled copies is multiplicative, not additive. Students make careful arguments about the scaling process (MP3), have opportunities to use tools like tracing paper or index cards strategically (MP5).

As students draw scaled copies and analyze scaled relationships more closely, encourage them to continue using the terms scale factor and corresponding in their reasoning.

Critique (orally and in writing) different strategies (expressed in words and through other representations) for creating scaled copies of a figure.
Draw a scaled copy of a given figure using a given scale factor.
Generalize (orally and in writing) that the relationship between the side lengths of a figure and its scaled copy is multiplicative, not additive.

Let’s draw scaled copies.

Geometry toolkits

Make sure students have access to their geometry toolkits, especially tracing paper and index cards.

I can draw a scaled copy of a figure using a given scale factor.
I know what operation to use on the side lengths of a figure to produce a scaled copy.

Building On