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Adding & Subtraction Fractions with unlike denom

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Adding & Subtraction Fractions with unlike denom

  1. 1. ractions ubtracting dding &
  2. 2. Adding & Subtracting Fractions Teacher Notes: <ul><li>Use this presentation to teach the steps for adding and subtracting fractions with unlike denominators. </li></ul><ul><li>It is assumed that students have a thorough understanding of the process for making equivalent fractions. </li></ul><ul><li>CLICK HERE to view a demonstration with opportunities for students to practice making equivalent fractions. </li></ul>
  3. 3. + We need a common denominator to add these fractions.
  4. 4. 7, 14, 21, 28, 35… 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 Count by 2's Count by 7's + We need a common denominator to add these fractions.
  5. 5. 7, 14, 21, 28, 35… 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 Count by 2's Count by 7's The first number IN COMMON that appears on both lists becomes the common denominator
  6. 6. + = x 2 x 2 = X 7 x 7 7 6 7 + 6 = 13 Add the numerators 13 Make equivalent fractions.
  7. 7. 5, 10, 15, 20, 25, 30, 35, 40, 45 7, 14, 21, 28, 35, 42, 49, 56, 63 Count by 7's Count by 5's + We need a common denominator to add these fractions.
  8. 8. = x 7 x 7 = X 5 x 5 15 7 + 15 + 7 = 22 Add the numerators 22 Make equivalent fractions.
  9. 9. 7, 14, 21, 28, 35, 42, 49, 56, 63 8, 16, 24, 32, 40, 48, 56, 64, 72 Count by 7's Count by 8's We need a common denominator to add these fractions. +
  10. 10. = x 7 x 7 = x 8 x 8 32 21 + 32 + 21 = 53 Add the numerators 53 Make equivalent fractions.
  11. 11. 3, 6, 9, 12, 15, 18, 21, 24, 27 5, 10, 15, 20, 25, 30, 35, 40, 45 Count by 3's Count by 5's + We need a common denominator to add these fractions.
  12. 12. X 3 = x 5 x 5 = x 3 9 10 + 9 + 10 = 19 Add the numerators 19
  13. 13. 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 11, 22, 33, 44, 55, 66, 77… Count by 3's Count by 11's + We need a common denominator to add these fractions.
  14. 14. = x 11 x 11 = X 3 x 3 15 22 + 15 + 22 = 37 Add the numerators 37 Make equivalent fractions.
  15. 15. 3, 6, 9, 12, 15, 18, 21, 24, 27 Count by 3's Count by 6's 6, 12, 18, 24,… + We need a common denominator to add these fractions.
  16. 16. = x 1 x 1 = X 2 x 2 4 1 + 4 + 1 = 5 Add the numerators 5 Make equivalent fractions.
  17. 17. 11, 22, 33, 44, 55, 66, 77… Count by 11's 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72 + We need a common denominator to add these fractions.
  18. 18. = x 11 x 11 = X 6 x 6 18 11 + 29 18 + 11 = 29 Add the numerators. Make equivalent fractions.
  19. 19. + We need a common denominator to add these fractions.
  20. 20. 9, 18, 27, 36, 45, 54, 63, 72, 81 5, 10, 15, 20, 25, 30, 35, 40, 45 Count by 5's Count by 9's + We need a common denominator to add these fractions.
  21. 21. 9, 18, 27, 36, 45, 54, 63, 72, 81 5, 10, 15, 20, 25, 30, 35, 40, 45 Count by 5's Count by 9's The first number IN COMMON that appears on both lists becomes the common denominator
  22. 22. + = x 5 x 5 = x9 x 9 36 35 36 + 35 = 71 Add the numerators. 71 Make equivalent fractions. 36 + 35 = 71 Add the numerators. Make equivalent fractions.
  23. 23. 12, 24, 36, 48, 60, 72, 84, 96 8, 16, 24, 32, 40, 48, 56, 64, 72, 79, 80, 88, 96 Count by 12's Count by 8's + We need a common denominator to add these fractions.
  24. 24. + = x 3 x 3 = x 2 x 2 19 10 + 9 = 19 Add the numerators. Make equivalent fractions. 9 10
  25. 25. 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 11, 22, 33, 44, 55, 66, 77… Count by 11's Count by 5's - We need a common denominator to subtract a fraction from another.
  26. 26. = x 5 x 5 = x 11 x 11 4 15 - 11 = 4 Subtract. Make equivalent fractions. - 15 11
  27. 27. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 … 10, 20, 30… Count by 2's Count by 10's - We need a common denominator to subtract one fraction from another.
  28. 28. = x 1 x 1 = x 5 x 5 2 5 – 3 = 2 Subtract. Make equivalent fractions. - 5 3
  29. 29. Try These A F E B C D
  30. 30. Answers On Next Slide <ul><li>Each click on the next slide reveals an answer. </li></ul><ul><li>Check your papers. </li></ul><ul><li>If you discover an incorrect answer, be able to explain your mistake. </li></ul>
  31. 31. Try These A F E B C D 17 27 19 20 10 9 41 28 26 21 13 12

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