Unit 2, Lesson 14
Find the Area of a Figure with Unknown Side Lengths
Grade 3
Preparation
Lesson Purpose
The purpose of this lesson is for students to calculate the areas of ungridded figures made of rectangles, including figures with unknown side lengths.
Lesson Narrative
In previous lessons, students found the areas of figures that were fully gridded with squares, and moved toward figures without a grid that had all their side lengths labeled. In this lesson, students use the strategies they have learned to decompose the figures into non-overlapping rectangles. They realize that not all measurements need to be given, and that some lengths can be determined given the rectangular structure of these figures.
- Engagement
- MLR8
- Critique (orally and in writing) a strategy for calculating an unknown side length.
- Explain (orally) strategies for calculating the area of a figure composed of rectangles, including figures with unknown side lengths.
- Let’s find the area of a figure with unknown side lengths.
Required Preparation
None
Teacher Reflection Questions
Reflect on which students have not shared their strategies in class lately. How can their insight or ways of thinking be highlighted in or tied to upcoming lessons?
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