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Learning Objective

Students will solve addition and subtraction story problems involving lengths measured in standard units, applying their understanding of place value and operations to find unknown lengths.

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Learning Standards

• 2.MD.B.5: Use addition and subtraction within 100 to solve word problems involving lengths that are given in the same units.
• 2.NBT.B.5: Fluently add and subtract within 100 using mental strategies.
• 2.OA.A.1: Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing.
• 2.OA.B.2: Fluently add and subtract within 20 using mental strategies.

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Key Vocabulary

• Length
• Unit (inch, foot, centimeter)
• Addition
• Subtraction
• Story problem
• Unknown (variable)
• Solve
• Equation

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Materials

• Number line 0–100
• Rulers and yardsticks (inches and feet)
• Pre-prepared story problem cards about lengths
• Whiteboards and markers per student
• Chart paper and markers
• Counters or linking cubes
• "Length Story Puzzle" worksheet

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Lesson Breakdown (90 minutes)

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Hook (10 min) – Launch and Warm-Up

Activity: "Length Detective"

• Display several classroom objects with visible length labels (desk: 30 inches; book: 12 inches; marker: 5 inches).
• Ask students: “If we put the marker and the book end to end, how long are they together? What if we take away the marker from the book’s length?”
• Write these as story problems on chart paper, but leave unknowns (e.g., “30 inches + ? inches = 45 inches”).
• Discuss what we know and what we need to find.

Purpose: Introduce the idea of solving story problems about lengths using addition and subtraction in a meaningful context.

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Learn (Explore)

Mini-lesson (I Do) (15 min)

• Model solving a length story problem using a number line:
  “A rope is 24 inches long. Another rope is 16 inches shorter than the first rope. How long is the second rope?”
• Draw the number line on the board. Show subtraction of 16 from 24 by counting back.
• Write the equation: 24 - 16 = ?
• Demonstrate using counters or cubes to physically represent the problem.
• Emphasize the key vocabulary and relate the story to the math equation.

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Guided Practice (We Do) (20 min)

• Distribute story problem cards related to lengths, each with addition or subtraction scenarios—e.g., “Lisa’s ribbon is 40 inches. She cuts 15 inches off to wrap a gift. How much ribbon is left?”
• Students work in pairs with rulers, cubes, or number lines.
• Circulate to support thinking, prompting students how to translate story problems to number sentences.
• Invite pairs to share their reasoning by writing equations on whiteboards, explaining their strategies.

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Independent Practice (You Do) (25 min)

• Hand out “Length Story Puzzle” worksheets:
  • Worksheets contain 6 mixed addition and subtraction story problems about lengths up to 100 inches, some requiring multiple-step reasoning.
  • Students solve independently using drawing, number lines, and equations.
• Encourage self-checking by reviewing whether their answers make sense in the context of the stories.
• Provide rulers if needed for reference.

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Closing (Synthesis & Discuss) (10 min)

• Gather students to share 2–3 different strategy solutions from their independent practice.
• Prompt questions: “How did your number line help you solve? Did anyone solve the same problem using a different method?”
• Reinforce vocabulary by having students create their own short story problem about length for a partner to solve next class.

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Fluency Focus (Throughout the Lesson)

• Quick addition and subtraction drills within 20 and up to 100, integrated into warm-up and guided practice.
• Use mental math strategies and number bonds to encourage fluency aligned to 2.NBT.B.5 and 2.OA.B.2.

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Differentiation

Group	Support Strategies	Extension Activities
Struggling learners	Use manipulatives and visuals more heavily; work with teacher in small group to scaffold vocabulary and problem steps.	Use smaller number ranges (less than 50) and repeated practicing addition/subtraction facts.
On-level learners	Scaffold with guided practice, encourage multiple strategies to solve problems.	Challenge with multi-step problems, e.g., involving measurement conversions between inches and feet.
Advanced learners	Provide open-ended problems that require creating and solving their own length story problems.	Introduce word problems involving simple unit conversions (e.g., 12 inches = 1 foot) and two-step problems.

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Assessment

• Formative: Observe student participation during guided practice, check whiteboard work for correct equations and strategy use.
• Independent worksheet: Collect and review “Length Story Puzzle” for accuracy and understanding of addition/subtraction in length contexts.
• Exit Ticket (5 min): One quick story problem posted on board. Students write number sentence and solve on mini-whiteboards before leaving.

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This lesson uses hands-on tools, visual aids, and collaborative activities to deepen place value and operation skills while solving real-world length problems, tightly aligned with Common Core standards 2.MD.B.5, 2.NBT.B.5, 2.OA.A.1, and 2.OA.B.2.