Use Side Lengths to find Area

Examples, solutions, and videos to help Grade 3 students learn how to find the area of a rectangle through multiplication of the side lengths.

Common Core Standards: 3.MD.5, 3.MD.6, 3.MD.7a, 3.MD.7b, 3.MD.7d

New York State Common Core Math Grade 3, Module 4, Lesson 8

Worksheets for Grade 3

Application Problem

Marnie and Connor both skip-count square units to find the area of the same rectangle. Marnie counts, “3, 6, 9, 12, 15, 18, 21.” Connor counts, “7, 14, 21.” Draw what the rectangle might look like, then label the side lengths and find the area.

Note: This problem reinforces G3–M4–Lesson 7 and sets the foundation for today’s Concept Development. Invite students to share their drawings and discuss how they are similar and how they are different.

Concept Development

Part 1: Relate side lengths to area.

Part 2: Use side lengths to find area.

Part 3: Use area and side length to find unknown side length.

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Lesson 8 Homework

1. Write a multiplication sentence to find the area of each rectangle.

2. Write a multiplication sentence and a division sentence to find the unknown side length for each rectangle.

2. On the grid below draw a rectangle that has an area of 32 square centimeters. Label the side lengths.

4. Charles draws a rectangle with a side length of 9 inches and an area of 27 square inches. What is the other side length? How do you know?

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