In previous lessons, students looked at the relationship between a figure and a scaled copy by finding the scale factor that relates the side lengths and by using tracing paper to compare the angles. This lesson takes both of these comparisons a step further.

- Students study
*corresponding distances*between points that are not connected by segments, in both scaled and unscaled copies. They notice that when a figure is a scaled copy of another, corresponding distances that are not connected by a segment are also related by the same scale factor as corresponding sides. - Students use protractors to test their observations about corresponding angles. They verify in several sets of examples that corresponding angles in a figure and its scaled copies are the same size.

Students use both insights—about angles and distances between points—to make a case for whether a figure is or is not a scaled copy of another (MP3). Practice with the use of protractors will help develop a sense for measurement accuracy, and how to draw conclusions from said measurements, when determining whether or not two angles are the same.

**Learning goals:**

- Identify corresponding lengths and angles that can show that a figure is not a scaled copy of another.
- Understand and explain how corresponding distances between points and corresponding angles behave in a figure and its scaled copies.

**Learning goals (student facing):**

- Let’s find relationships between scaled copies.

**Learning targets (student facing):**

- I can use corresponding distances and corresponding angles to tell whether one figure is a scaled copy of another.
- When I see a figure and its scaled copy, I can explain what is true about corresponding angles.
- When I see a figure and its scaled copy, I can explain what is true about corresponding distances.

**Required materials:**

- geometry toolkits

**Required preparation:**

- Make sure students have access to their geometry toolkits, especially rulers and protractors.

**Glossary:**

- Access the complete Grade 7 glossary.

Adapted from Open Up Resources under CC BY license. All adaptations copyright LearnZillion.