Lesson 19
Trash Talk
Lesson Purpose
Lesson Narrative
In previous lessons, students have learned to use the standard algorithm to multiply whole numbers including a threedigit and a twodigit number. The purpose of this lesson is to apply those techniques to a situation involving areas related to the Great Garbage Patch. The measurements are given in kilometers so students review, in the first activity, how long a kilometer is. Then, students calculate the area of states to get a sense for the size of the Great Garbage Patch. One of these calculations is a product of two threedigit numbers. After this brief interlude solving problems about area, students return to volume for the final two lessons. The area calculations for the states showed the importance of estimation since finding the exact products requires careful calculations whereas a quick estimate shows that the area of New Mexico is less than the area of the Great Garbage Patch. This estimation builds on student learning from the previous activity and then next two lessons combine estimation, volume, and trash.
 Representation
 MLR8
Activity 1: Square Kilometers
Learning Goals
Teacher Facing
 Use multiplication to solve problems about the area of the Great Garbage Patch.
Student Facing
 Let’s multiply to solve problems about the area of the Great Garbage Patch.
Required Materials
Materials to Gather
Required Preparation
Lesson Timeline
Warmup  10 min 
Activity 1  10 min 
Activity 2  25 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
In what ways did students extend and apply their understanding of multiplication and area throughout the lesson?
Suggested Centers
 Mystery Number (1–4), Stage 6: Decimals (Supporting)
Print Formatted Materials
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Additional Resources
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