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Published byGloria Weaver Modified over 8 years ago

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Subtracting Integers with Counters

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How to subtract integers with counters 1.Rewrite the problem – Keep the first number the same – Change the problem from subtraction to addition – Make the last number its opposite 2.Lay out your counters to represent the problem. 3.Get rid of zero pairs 4.Count up what you have

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Here’s how you rewrite the problem! -8 – 7 -8 + -7 -8 stays the same Subtraction becomes addition 7 changes to its opposite -7 Additive Inverse Two integers that are opposite of each other are additive inverses. The sum of any number and its additive inverse is zero.

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5 - -6 5 positive units+6 positive units Get rid of pairs. What do you have left? 11 positive units Answer = 11 Now rewrite the problem. 5 + +6

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-10 - -3 10 negative units+3 positive units Get rid of pairs. What do you have left? 7 negative units Answer = -7 Now rewrite the problem. -10 + +3

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5 - 13 5 positive units+13 negative units Get rid of pairs. What do you have left? 8 negative units Answer = -8 Now rewrite the problem. 5 + -13

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You try & rewrite these problems 1.-4 – 8 = 2.9 – 17 = 3.3 - -5 = 4.6 – 10 = 5.-8 - - 17 = 1. -4 + -8 = 2. 9 + -17 = 3. 3 + 5 = 4. 6 + -10 = 5. -8 + 17 = Rewritten Problems Now follow adding rules or use algebra tiles to solve! 1. -12 2. -8 3. 8 4. -4 5. 9

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Solve these practice problems! 1.-5 - -4 = 2.4 - -7 = 3.-12 – 4 = 4.9 - -5 = 5.-5 - -9 = 6.-10 – 8 = 7.-4 - -4 = 8.-12 -3 = 1.-1 2.11 3.-16 4.14 5.4 6.-18 7.0 8.-15

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Word Problems 1.A submarine is situated at 450 feet below sea level and sinks 75 feet. What is the new position of the submarine? -450 – 75 = -525 feet The new position of the submarine was 525 feet below sea level. 2.The temperature at 8pm was 6°F. At 2am the temperature decreased 13 degrees. What was the temperature at 2am? 6 – 13 = -7°F The temperature at 2am was -7°F.

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