K-12 Teaching and Learning From the UNC School of Education

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Learning outcomes

Students will:

  • solve math problems involving addition and subtraction of whole numbers involved in the purchase and resale of a dog using paper and pencil, estimation, mental computation, manipulatives, and calculators.
  • assess the effectiveness of each problem solving method by evaluating each for practicality and accuracy.
  • choose the appropriate operations to solve practical problems involving a series of money transactions surrounding the purchase and resale of a dog.
  • explore the relationship between income and expenses.
  • apply mathematics to make decisions concerning personal finances.

Teacher planning

Time required for lesson

1 Hour


  • play money
  • prop (toy dog)
  • checkbook registers
  • chart paper
  • markers
  • calculators
  • Buy and Sell the Dog attachment

Technology resources



State the problem using the prop. Relate topic problem to other every day examples.


Group work or individual work is suggested as an action plan for this lesson.

  1. Have students divide into groups of 2-3 (depending on availability of materials and class size).
  2. Instruct each group to solve the problem in a different way. For example, ask group 1 to solve the problem using play money; group 2, using checkbook registers; group 3, using calculators; and group 4, using pencil and paper (make sure there is even representation of all methods of solving the problem).
  3. Instruct all groups to make notes detailing their money transactions, including all gains and loses along the way.
  4. When all groups have completed the activity, share results as a whole class.
  5. In discussion, have students evaluate the effectiveness of each method based on practicality and accuracy.
  6. As a method of closure, enlist students to brainstorm and come up with other methods of solving this or other math problems involving money.

(Other possibilities for solving the problem include making number lines or using pictographs.)


  • Assessment for this activity is mainly observational. Evaluation of student understanding is based on accuracy (whether of not they get the answer to the problem correct) and thoroughness of presentation and discussion.
  • Instruct (a) representative(s) from each group to present their transactions to the whole class, outlining their buying and selling of the dog.
  • After providing the correct answer, ask students to evaluate the accuracy and efficiency of their particular method for solving the problem; be sure they include pros and cons.
  • As students present their findings, check for understanding of the math involved; ask questions about their findings.

  • Common Core State Standards
    • Mathematics (2010)
      • Grade 4

        • Operations & Algebraic Thinking
          • 4.OAT.3Solve multistep word problems posed with whole numbers and having whole-number answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown...

North Carolina curriculum alignment

Mathematics (2004)

Grade 5

  • Goal 5: Algebra - The learner will demonstrate an understanding of patterns, relationships, and elementary algebraic representation.
    • Objective 5.02: Use algebraic expressions, patterns, and one-step equations and inequalities to solve problems.
    • Objective 5.03: Identify, describe, and analyze situations with constant or varying rates of change.