Students will investigate the concept of areas of rectangular figures by using area models to represent the distributive property. They will also use models to find the area of a rectangle with side lengths a and b + c is the same as the sum of a x b and a x c.

- slide 1 of 6
**Lesson Objective:**The lesson is aligned to the Common Core State Standards for Mathematics – 3.MD.7c Geometric Measurement – Use area models to represent the distributive property.**Materials Required:**graph paper, calculator - slide 4 of 6
Now look at Rectangle 2 and Rectangle 3 shown on the grid.

5. Rectangle 2 has Side a and Side b. Identify the lengths of the two sides of Rectangle 2.

6. Rectangle 3 has Side a and Side c. Identify the lengths of the two sides of Rectangle 3.

7. Find the areas of Rectangle 2 and Rectangle 3.

8. Complete the chart.

9. What is the area of Rectangle 1?

10. What is the sum of the areas of Rectangle 2 and Rectangle 3?

11. Compare the area of Rectangle 1 with sides a and (b + c) and the sum of the areas of Rectangle 2 and Rectangle 3.

12. Write a statement about the comparison.

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### Answers:

1. 5 units

2. 7 units

3. 35 square units

5. 5 units and 3 units

6. 5 units and 4 units

7. 15 square units and 20 square units

9. 35 square units

10. 15 + 20 = 35 square units

11. The area of Rectangle 1 with sides 5 and (3 + 4) is 35. The sum of the areas of Rectangle 2, 15 square units, and Rectangle 3, 20 square units, is 35 square units.

12. The area of Rectangle 1 is equal to the sum of the areas of Rectangle 2 and Rectangle 3.

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### Download Lesson with Individual or Group Work

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**please download it here.**Group work is at the end of the lesson.

#### Grade 3 Math Lessons on Geometric Measurement

- Finding the Area of Figures using Unit Squares: Grade 3 Math Lesson
- Finding the Area of Figures using Unit Squares: 3rd Grade Math
- 3rd Grade Math: Finding the Area of Rectangular Figures using Multiplication
- Finding the Area of Rectangular Figures in Real World Mathematical Problems: Grade 3 Lesson
- Finding Area using a Model of the Distributive Property: Math Lesson for Grade 3
- Finding the Area with Decomposition and Addition: 3rd Grade Math Lesson with Assessment