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7.8 Adding Positive and Negative Numbers Miss Hepner

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Math Message

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Mental Math Reflexes Use, or = to compare numbers 1.-5 and -7 2.2.5 and -1 3.- 8/4 and -2

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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?

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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)

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

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

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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.

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

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

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

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

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

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

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

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

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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

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

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

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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.

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

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

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

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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

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

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