Subtracting Integers

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Subtracting Integers

  1. 1. On a chip board
  2. 2. So let’s subtract -5 - -3 Put on 5 red chipsSince we’re subtracting, weneed to take chips OFF the board Take off 3 red chips (in order to subtract - 3) So, -5 - -3 =-2
  3. 3. Now let’s subtract -3 - -5 Put on 3 red chipsHow can we subtract 5 redchips when we only have 3? ADD TWO ZERO PAIRS! Now you can take off the five red chips. -3 - -5 = 2
  4. 4. Remember, one positiveand one negative make a ZERO PAIR
  5. 5. Say you wanted to show “+5” on a chip board. You could just use 5 yellow chipsor 5 yellow chips and a zero pairor 5 yellow chips and 2 zero pairs This is very important for subtraction!
  6. 6. Now let’s subtract 2 - 3 Put on 2 yellow chipsHow can we take away 3yellow chips when we only have 2? How many zero pairs do we need? Now you can take away 3 yellow chips. 2 - 3 = -1
  7. 7. Try subtracting -4 - -6 What should we do first?Do we have enough to subtract -6? No, so how many zeropairs do we need to add?Now, what do we take away? -4 - -6 = 2
  8. 8. Let’s try 5 - -3 What should we do first? Do we have enough to subtract -3?We need to take off 3 red chips, and we don’t have ANY! So, how many zero pairs do we need to add? Now, what do we take away? 5- -3 = 8
  9. 9. Let’s try one more 5 - 7 What should we do first?Do we have enough to subtract 7? No, so how many zeropairs do we need to add?Now, what do we take away? 5 - 7 = -2
  10. 10. 1. Solve 5 – 3Explain in words:2. Solve -5 – (-3)Explain in words:
  11. 11. 3. Solve -5 – 3Explain in words:1. Start with -52. Add 3 zero pairs3. Remove 3 positives
  12. 12. 4. Solve 5 – (-3)Explain in words:5. Solve -4 – (-7)Explain in words:
  13. 13. 6. Solve -3 – (-4)Explain in words:7. Write the subtractionproblem that is modeledin the box. + + + + +
  14. 14. 1. What does it mean to add a “zero pair”?2. Does adding a “zero pair” change the difference?
  15. 15. -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 11. Model on the number line and solve. -4 – 3 = -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 2. Model on the number line and solve. 6 – 8 =
  16. 16. Rules for adding integers:• Same signs – ADD and keep the sign.• Different signs – SUBTRACT and take the sign from the number that “has more” (or is bigger in absolute value.
  17. 17. Rules for subtracting integers:SUBTRACTION IS ICKY! So:1. Keep the first number the same.2. Change the subtraction sign to addition.3. Make the second number its opposite.4. Use the addition rules. Keep it! Change it! Opposite it!

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