Lesson plan

# 1. Write multiplication and division equations with unknowns to solve problems (C)

teaches Common Core State Standards CCSS.Math.Content.3.OA.A.3 http://corestandards.org/Math/Content/3/OA/A/3
teaches Common Core State Standards CCSS.Math.Practice.MP2 http://corestandards.org/Math/Practice/MP2

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Lesson objective: Understand that a relationship exists between the three whole numbers in a multiplication and division equation that helps to identify a missing number to make an equation true.

Students bring prior knowledge of multiplication and division from 3.OA.A.1, 3.OA.A.2 and 3.OA.A.3. This prior knowledge is extended using the relationship between multiplication and division as students write and solve related multiplication and division equations with unknowns. A conceptual challenge students may encounter is understanding how to represent these relationships using arrays and area models.

The concept is developed through work with arrays and area models, which represent multiplication and division as two factors (number of rows and number of columns) and the product (total number of square units).

This work helps students deepen their understanding of operations because we can use the relationship between multiplication and division to find unknown numbers in equations.

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively) as they decontextualize this problem as they write multiplication and division equations to represent it.

Key vocabulary:

• area model
• column
• equation
• rectangular array
• row

Special materials needed:

• grid paper
• manipulatives such as counters or square tiles