Unit 2, Lesson 12
Area and Addition
Grade 3
Preparation
Lesson Narrative
Students first decompose a rectangle into parts to see that area is additive. Then students decompose into rectangles a figure composed of rectangles in any way that makes sense to them, find the areas of those rectangles, and add them together to find the area of the figure. Students learn that parentheses are grouping symbols that can be used in expressions or equations, and they use them to represent how they decompose the figure into rectangles. The work of this lesson connects to previous work because students find the areas of rectangles within the figure before adding to find the total area of the figure.
- Action and Expression
None
- Explain (orally) a strategy for finding the area of a gridded figure composed of rectangles.
- Present (using words or other representations) a strategy for finding the area of a gridded “figure” composed of rectangles.
- Let’s find the area of a figure made up of rectangles.
Required Preparation
None
Teacher Reflection Questions
Which students came up with an unexpected strategy in today’s lesson? What are some ways you can be more open to the ideas of each and every student?