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Unit 2 - Lesson 5 - Grade 8: Illustrative Mathematics

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Grade 8 Unit 2
Lesson 5: More Dilations
CC BY 2021 Illustrative Mathematics®
Grade 8 Unit 2
Lesson 5: More Dilations
CC BY 2021 Illustrative Mathematics®
Lesson: More Dilations

Many Dilations of a Triangle (Warm Up)

All of the triangles are dilations of Triangle D. The dilations use the same center P, but different scale factors.
1.

What do Triangles A, B, and C have in common? What do Triangles E, F, and G have in common? What does this tell us about the different scale factors used?


Info Gap: Dilations

Your teacher will give you either a problem card or a data card. Do not show or read your card to your
partner.
If your teacher gives you the problem card:

1. Silently read your card and think about what
information you need to be able to answer the question.

2. Ask your partner for the specific information that you need.

3. Explain how you are using the information to solve the problem.

Continue to ask questions until you have enough information to solve the problem.
If your teacher gives you the data card:

1. Silently read your card.

2. Ask your partner “What specific information do you need?” and wait for them to ask for information.

If your partner asks for information that is not on the card, do not do the calculations for them. Tell them you don’t have that information.

3. Before sharing the information, ask “Why do you need that information?” Listen to your partner’s reasoning and ask clarifying questions.
2.

Read the problem card and solve the problem independently.

Share the data card and discuss your reasoning.
Pause here so your teacher can review your work. Ask your teacher for a new set of cards and repeat the activity, trading roles with your partner.
Cool Down: Identifying a Dilation

Identifying a Dilation

The smaller triangle is dilated to create the larger triangle. The center of dilation is plotted, but not labeled.
3.

Describe this dilation. Be sure to include all of the information someone would need to perform the dilation.