Curriculum / Math / 3rd Grade / Unit 4: Area / Lesson 12
Math
Unit 4
3rd Grade
Lesson 12 of 14
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Recognize area as additive. Find the area of a composite figure as shown on a grid or with all side lengths labeled.
The core standards covered in this lesson
3.MD.C.7.D — Recognize area as additive. Find areas of rectilinear figures by decomposing them into non-overlapping rectangles and adding the areas of the non-overlapping parts, applying this technique to solve real world problems.
The essential concepts students need to demonstrate or understand to achieve the lesson objective
Suggestions for teachers to help them teach this lesson
At some point in the lesson, students might suggest covering a composite figure with a larger rectangle and subtracting the voided area, e.g., by computing $$(4\times5)-(2\times3)$$ for Anchor Task #1. This is certainly a valid strategy, but not one that all students must show success with. Thus, discuss it in this lesson if students seem ready to talk about it or many students naturally gravitate toward it, or wait until a later lesson (if at all) to introduce it.
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Tasks designed to teach criteria for success of the lesson, and guidance to help draw out student understanding
Mr. Silver is thinking about building an L-shaped desk to use in his classroom. Here is the blueprint he made:
What’s the area, in square units, of the desk? Try to work it out without counting each square individually.
Grade 3 Mathematics > Module 4 > Topic D > Lesson 13 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..
What is the area of the figure below? The tick marks around the figure are 1 unit apart.
3.MD.7 - About the Math, Learning Targets, and Rigor is made available by the Howard County Public School System under a CC BY-NC-SA 4.0 license. © 2013-2014 Elementary Mathematics Office Howard County Public School System. Accessed Jan. 2, 2019, 3:15 p.m..
Find the area, in square meters, of the shaded figure.
Problem Set
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A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved
Find the total area, in square units, of the shaded figure below.
An example response to the Target Task at the level of detail expected of the students.
The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.
Extra Practice Problems
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Lesson 11
Lesson 13
Topic A: Understanding Concepts of Area
Understand that area is an attribute of plane figures that is a measure of how much flat space an object takes up. Find the area of a figure using pattern blocks, which can be used as concrete non-standard units.
3.MD.C.5 3.MD.C.6
Understand that area is measured using square units. Find the area of a figure using square tiles.
Find the area of a rectangle by counting unit squares on grids.
Find the area of a rectangle with incomplete information about its rows and columns of square units.
3.MD.C.6 3.MD.C.7.A
Find the area of a rectangle that has been superimposed over a grid.
Find the area of a rectangle through multiplication of the side lengths.
3.MD.C.7.A 3.MD.C.7.B
Understand standard units for measuring area, including square inches, square centimeters, square feet, and square meters, and choose an appropriate unit to measure the area of various rectangles.
3.MD.C.6
Measure the side lengths of a rectangle to find its area.
3.MD.C.7.B
Solve word problems involving area.
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Topic B: The Distributive Property and Composite Area
Compose and decompose a rectangle, seeing and making use of the idea that the sum of the areas of the decomposed rectangle is equal to the area of the composed rectangle.
3.MD.C.7.C
Apply the distributive property as a strategy to find the total area of a large rectangle.
3.MD.C.7.D
Recognize area as additive. Find the area of a composite figure when not all dimensions are given.
Recognize area as additive. Find the area of a complex composite figure.
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