Lesson plan

# 10. Solve addition and subtraction problems involving mass (A)

teaches Common Core State Standards CCSS.Math.Content.3.MD.A.2 http://corestandards.org/Math/Content/3/MD/A/2
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4
teaches Common Core State Standards CCSS.Math.Practice.MP5 http://corestandards.org/Math/Practice/MP5

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Lesson objective: Solve problems using the number line to show addition and subtraction strategies.

This lesson provides an opportunity for students to apply their knowledge and understanding of addition and subtraction to a real-life situation. Students are asked to show on the number line a correct strategy for solving the problem.

Key Concept students will use:

• representations and drawings to solve one-step situational problems involving addition and subtraction of mass.

Skills students will use:

• place value understanding to add and subtract using a variety of strategies (Grade 3, Unit 3)
• a number line to solve many types of addition and subtraction problems (Grade 2, Unit 2)
• representations of a three-digit number as hundreds, tens, and ones, from left to right. (Grade 2, Unit 6)

Students engage in Mathematical Practice 1 (make sense of problems and persevere in solving them) as they use the number line to understand the problem and the meaning of the question. Students engage in Mathematical Practice 4 (model with mathematics) as they write number equations to describe how they used the number line.

Key vocabulary:

• grams
• kitchen gram scale
• number line
• pan balance

Special materials needed:

• kitchen gram scale
• number line for demonstration (0 to 2,000)
• pan balance scale and gram weights