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Add 21/42 and 45/80

21/42 + 45/80 is 17/16.

Steps for adding fractions

  1. Find the least common denominator or LCM of the two denominators:
    LCM of 42 and 80 is 1680

    Next, find the equivalent fraction of both fractional numbers with denominator 1680
  2. For the 1st fraction, since 42 × 40 = 1680,
    21/42 = 21 × 40/42 × 40 = 840/1680
  3. Likewise, for the 2nd fraction, since 80 × 21 = 1680,
    45/80 = 45 × 21/80 × 21 = 945/1680
  4. Add the two like fractions:
    840/1680 + 945/1680 = 840 + 945/1680 = 1785/1680
  5. 1785/1680 simplified gives 17/16
  6. So, 21/42 + 45/80 = 17/16
    In mixed form: 11/16

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