Adding & Subtracting Integers

Unit: Mastering Integers Together

Lesson 2 of 5

Duration: 30 minutes

Class Size: 30 students

Grade: 9th Grade

Curriculum Alignment: Common Core State Standards (CCSS) – Mathematics

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Standards Addressed

• CCSS.MATH.CONTENT.7.NS.A.1
  Apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram.

• CCSS.MATH.PRACTICE.MP1
  Make sense of problems and persevere in solving them.

• CCSS.MATH.PRACTICE.MP3
  Construct viable arguments and critique the reasoning of others.

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Learning Objectives

By the end of this lesson, students will be able to:

1. Explain and apply the rules for adding and subtracting positive and negative integers.
2. Use the number line to visually represent addition and subtraction of integers.
3. Solve real-world problems involving integer operations.
4. Collaborate with peers to reinforce understanding through group activities and games.

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Materials Needed

• Whiteboard and markers
• Number line posters or projected digital number lines
• Colored integer chips or counters (red for negative, blue for positive)
• Student worksheets with practice problems and word problems
• "Integer War" card game materials (integer cards, or prepared integer flashcards)

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Lesson Breakdown

1. Warm-Up & Review (5 minutes)

• Begin with a quick verbal Q&A: Ask students to recall the meaning of positive and negative integers.
• Demonstrate addition and subtraction on the number line with a simple example:
  • Example: 3 + (-5), and 4 - 7.
• Emphasize direction and magnitude on the number line—moving right for positive, left for negative.

Teacher Tip: Use a large visual number line displayed where all can see.

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2. Direct Instruction: Rules for Adding & Subtracting Integers (7 minutes)

• Clearly state the rules:

  • Adding integers with the same sign: add their absolute values and keep the sign.
  • Adding integers with different signs: subtract the smaller absolute value from the bigger absolute value and keep the sign of the integer with the larger absolute value.
  • Subtracting an integer is the same as adding its opposite.

• Use a few step-by-step examples on the board, modeling with colored chips to represent positive and negative values.

  • Example 1: (-3) + (-7)
  • Example 2: 6 + (-9)
  • Example 3: 5 - (-2)

• Connect to the number line as a visual explanation for each example.

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3. Guided Group Activity: Real-Life Scenarios (8 minutes)

• Split the class into groups of 5 (6 groups total).
• Provide each group with a real-life scenario worksheet involving integer operations (examples below).
• Groups discuss and solve the problems together, using number lines and chips as needed.

Sample Real-Life Scenarios:

• Hiking: Gain or loss in elevation (+ and – integers)
• Banking: Deposits and withdrawals affecting balance
• Temperature: Changes in temperature through day and night

Teacher Role: Circulate to prompt reasoning, clarify misunderstandings, and encourage collaboration (MP3).

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4. Game: Integer War (8 minutes)

• Each group plays Integer War, which helps reinforce addition and subtraction of integers.

• How to play:

  • Students draw two integer cards and determine the sum or difference.
  • Highest result wins the round.
  • Players must explain their calculation process aloud before winning the round.

• This fosters peer teaching and verbal reasoning (MP1, MP3).

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5. Exit Ticket & Assessment (2 minutes)

• Hand out a quick 3-question exit ticket:

  1. Calculate: (-8) + 12
  2. Calculate: 7 - (-4)
  3. Explain why subtracting a negative is the same as adding a positive (in student’s own words).

• Collect these to gauge understanding and target for next lesson.

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Differentiation

• Supports for Struggling Students:
  Use number lines and chips heavily; pair with a stronger peer in group work.

• Challenge for Advanced Students:
  Provide problems involving three or more integer operations and ask them to create their own real-world integer problem.

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Reflection & Next Steps

• Highlight the importance of integer operations in solving everyday problems.
• Preview next lesson: Multiplying and Dividing Integers – building on today’s foundation.

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Teacher Notes

• Monitor timing carefully for smooth transitions.
• Encourage students to verbalize their reasoning to deepen understanding and foster mathematical discourse.
• Use the game as both formative assessment and engagement tool.

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End of Lesson Plan