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3-GM-2-2

Page history last edited by Tashe Harris 6 years, 2 months ago

3.GM.2.2 Develop and use formulas to determine the area of rectangles. Justify why length and width are multiplied to find the area of a rectangle by breaking the rectangle into one unit by one unit squares and viewing these as grouped into rows and columns.

In a Nutshell

In third grade students are learning to think multiplicatively. This objective gives students the opportunity to connect what they know about multiplication and apply it when finding the area of a shape. They will first use square units to help them find the area of a rectangle. Then they will recognize that the area of shape looks similar to an array, which means multiplication can be used to find the area of rectangles.

Student Actions	Teacher Actions
Make conjectures about the area of rectangles by covering them with 1x1 square unit tiles. Demonstrate a deep and flexible understanding as they determine the formula for finding the area based on the idea that rectangles can be made into arrays. Develop mathematical reasoning as they apply the formula for area with the understanding that columns multiplied by rows (arrays) are the same as length multiplied by width (area).	Pose purposeful questions to help students recall prior knowledge and justify their thinking. Questions may include: What formula can we use to find the area of a shape? How can we prove the area of a shape? Elicit student thinking by prompting discussion that encourages students making connections to other math concepts, such as finding the product using an array. Implement tasks that challenge students to solve for the area in a variety of ways.
Key Understandings	Misconceptions
The area is the total surface within a rectangle. Rectangles can be broken down by 1x1 units, or square units. The number of 1x1 squares must correspond to the length and width. Ex: 4x5 rectangle would have 5 rows of 4 square units. The area of a shape can be found by adding the squares inside the rectangle. Finding the area is quicker when you multiply the length by the width. Labels are important to understand the size of the rectangle.	The area of the rectangle is the same as the perimeter or that they are interchangeable terms. The square units within a rectangle are unrelated to the length and width measurements.