Subtracting Integers with Counters

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Subtracting Integers with Counters
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How to subtract integers with counters

• Rewrite the problem
• Keep the first number the same
• Change the problem from subtraction to addition
• Make the last number its opposite
• Lay out your counters to represent the problem.
• Get rid of zero pairs
• Count up what you have

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Heres how you rewrite the problem!

• -8 7
• -8 -7

7 changes to its opposite -7
-8 stays the same
Subtraction becomes addition
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 6
Now rewrite the problem.
5 positive units

6 positive units
Get rid of pairs. What do you have left?
11 positive units
Answer 11
5
-10 - -3
-10 3
Now rewrite the problem.
10 negative units

3 positive units
Get rid of pairs. What do you have left?
7 negative units
Answer -7
6
5 - 13
5 -13
Now rewrite the problem.
5 positive units

13 negative units
Get rid of pairs. What do you have left?
8 negative units
Answer -8
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You try rewrite these problems
Now follow adding rules or use algebra tiles to
solve!
Rewritten 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

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

• 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.
• The temperature at 8pm was 6F. At 2am the
  temperature decreased 13 degrees. What was the
  temperature at 2am?
• 6 13 -7F
• The temperature at 2am was -7F.