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7.8 Adding Positive and Negative Numbers

7.8 Adding Positive and Negative Numbers. Miss Hepner. Math Message. Mental Math Reflexes. Use <, >, or = to compare numbers -5 and -7 2.5 and -1 - 8/4 and -2. Adding Positive and Negative Numbers. Objective: To develop rules for adding positive and negative numbers

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7.8 Adding Positive and Negative Numbers

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  1. 7.8 Adding Positive and Negative Numbers Miss Hepner

  2. Math Message

  3. Mental Math Reflexes Use <, >, or = to compare numbers • -5 and -7 • 2.5 and -1 • - 8/4 and -2

  4. Adding Positive and Negative Numbers • Objective: To develop rules for adding positive and negative numbers • Lesson Essential Question: How do I add positive and negative numbers and what strategy can I use?

  5. 3 Strategies • Today we will learn 3 different strategies to add positive and negative numbers. You choose the strategy that works best for you! The three strategies include: 1. Pair and cancel (using + and – tokens) 2. Number line method 3. Subtract and Highest Sign (team and battle)

  6. How do I add positive and negative numbers? Strategy #1 -9 + 5 Pair and Cancel Method: Take nine negative tokens and five positive tokens

  7. How do I add positive and negative numbers? Strategy #1 -9 + 5 Pair a negative token with a positive token

  8. How do I add positive and negative numbers? -9 + 5 The paired tokens cancel each other out! Count the left over tokens and there is your answer.

  9. How do I add positive and negative numbers? -9 + 5 = -4

  10. Let’s try another example using Strategy #1 -3 + 6 Pair and Cancel Method: Take nine negative tokens and five positive tokens

  11. -3 + 6 Pair a negative token with a positive token Count your left over tokens and that is your answer.

  12. How do I add positive and negative numbers? -3 + 6 = 3

  13. Another way to look at it: -9 + 5 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 Number Line Method

  14. Another way to look at it: -9 + 5 = -4 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1

  15. Strategy #2- Number Line -5 + -3 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 Number Line Method

  16. Strategy #2- Number Line -5 + -3 = -8 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1

  17. Another way to think about it… • Subtract the two number and take the sign of the larger: -9 + 5 = 9 – 5 = 4 (take the sign of the larger) Answer = -4 Subtract and Highest Sign Method

  18. Pair and Cancel Method -3 + 7 Take three negative tokens and seven positive tokens

  19. How do I add positive and negative numbers? -3 + 7 Pair a negative token with a positive token

  20. How do I add positive and negative numbers? -3 + 7 The paired tokens cancel each other out! Count the left over tokens and there is your answer.

  21. How do I add positive and negative numbers? -3 + 7 = 4

  22. Number Line Method -3 + 7 -3 -2 -1 0 1 2 3 4 5 6 7

  23. Another way to look at it: -3 + 7 = 4 -3 -2 -1 0 1 2 3 4 5 6 7

  24. Subtract and Highest Sign Method • Subtract the two number and take the sign of the larger: -3 + 7 = -3 + 7 = 4 (take the sign of the larger) Answer = 4

  25. Practice: • 7 – 10 • -4 + 12 • 9 – 15 • -3 + 8 • -6x + 2x

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