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Subtract 1/40 from 21/42

21/42 - 1/40 is 19/40.

Steps for subtracting fractions

  1. Find the least common denominator or LCM of the two denominators:
    LCM of 42 and 40 is 840
  2. For the 1st fraction, since 42 × 20 = 840,
    21/42 = 21 × 20/42 × 20 = 420/840
  3. Likewise, for the 2nd fraction, since 40 × 21 = 840,
    1/40 = 1 × 21/40 × 21 = 21/840
  4. Subtract the two fractions:
    420/840 - 21/840 = 420 - 21/840 = 399/840
  5. After reducing the fraction, the answer is 19/40

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