Solving Story Problems

Subject

Mathematics

Learning Objective

Students will be able to represent and solve one- and two-step addition and subtraction story problems within 100, using diagrams or equations. They will apply strategies based on place value and the relationship between addition and subtraction without requiring decomposition of tens.

Learning Standards

• 2.NBT.B.5: Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
• 2.OA.A.1: Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, using drawings and equations with a symbol for the unknown number to represent the problem.
• 2.OA.B.2: Fluently add and subtract within 20 using mental strategies. (Supports fluency focus)

Key Vocabulary

• Addition
• Subtraction
• Sum
• Difference
• Altogether
• More than
• Less than
• Equation
• Unknown
• Diagram
• Step (one-step, two-step)

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Hook (Launch, Warm-Up) — 10 minutes

Activity: "Math Detective Story"

1. Present a short, engaging story involving addition or subtraction (e.g., “Sally has 45 apples. She gave 23 apples to her friend. How many apples does Sally have now?”).
2. Ask students what information they know and what they need to find out.
3. Have students turn and talk with a partner to discuss how they might figure out the answer.

Purpose: Activate prior knowledge and set a real-world context for story problems.

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Learn (Explore)

Mini-lesson (I Do) — 15 minutes

1. Introduce using diagrams and equations:
   • Model how to translate a one-step problem into a number sentence (equation) and a simple diagram (e.g., bar model or part-part-whole).
   • Show a subtraction problem within 100 and work through it step-by-step without decomposing tens, focusing on counting back or place value strategies.
2. Introduce two-step problems:
   • Demonstrate solving a problem with two actions (e.g., “John had 50 marbles, he gave 20 to Mary, and then found 15 more.”)
   • Write corresponding equations and draw diagrams, emphasizing that students can solve these in the order the problem is presented.

Model thinking aloud, highlighting the use of vocabulary and reasoning from place value.

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Guided Practice (We Do) — 25 minutes

Collaborative Small Group Work:

• Divide students into pairs or groups of three (4-5 groups). Provide each group with 2-3 story problems to solve together.
• Problems will be a mixture of one-step and two-step addition and subtraction within 100, emphasizing context (altogether, more than, less than).
• Encourage students to:
  • Draw diagrams (bar models, number lines)
  • Write number sentences with unknowns
  • Talk through their reasoning aloud
• Circulate and scaffold: guide groups to use place value strategies, clarify vocabulary, and ensure all students participate actively.

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Independent Practice (You Do) — 20 minutes

Individual Workbook/Worksheet Activity:
Students solve a set of 5 story problems on their own, focusing on:

• Using diagrams or equations
• Solving within 100 without decomposing tens
• One-step and two-step problems
  Examples:
• “There are 65 candies in a jar. 23 candies were eaten. How many candies are left?”
• “Lilly has 38 crayons. She buys 25 more and gives 17 to her friend. How many crayons does she have now?”

Encourage students to draw and write equations for every problem.

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Closing (Synthesis, Discuss) — 10 minutes

• Bring the class back together.
• Invite 3-4 volunteers to share one problem they solved, explaining the diagram and equation they used.
• Highlight correct use of vocabulary and reasoning strategies.
• Summarize the key strategies learned: using place value to add/subtract, writing story problems as diagrams and equations, solving one- and two-step problems.

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Fluency Focus — 5 minutes

Quick Mental Math Challenge:

• Flash simple addition and subtraction facts within 20 on the board (e.g., 8 + 7, 15 - 6) for quick response.
• Helps reinforce fluency (standard 2.OA.B.2), supporting understanding of larger problems.

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Differentiation

• For struggling learners:
  • Provide simplified one-step problems with visual supports (number lines, counters).
  • Use sentence frames to help write equations (e.g., “___ minus ___ equals ___”).
  • Pair with a peer buddy for guided practice.
• For advanced learners:
  • Challenge with two-step problems that mix addition and subtraction contextually.
  • Introduce a mystery number in equations for students to solve (e.g., 45 - ___ = 23).
  • Encourage explaining their reasoning in writing or orally.

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Assessment

• Formative: Observe during group work and discussions; check worksheets for correct use of diagrams and equations.
• Cool Down: Exit ticket with 2 quick story problems to solve individually (one one-step, one two-step).
• Follow-up: Use quick quizzes during next lesson to reinforce fluency and problem-solving accuracy.

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This lesson plan not only rigorously aligns with Common Core standards 2.NBT.B.5, 2.OA.A.1, and 2.OA.B.2 but also integrates active learning, scaffolding, and collaboration to make math story problems engaging and accessible for all 2nd-grade learners.