Subtract 12/40 from 21/42
21/42 - 12/40 is 1/5.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 40 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 42 × 20 = 840,
21/42 = 21 × 20/42 × 20 = 420/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
12/40 = 12 × 21/40 × 21 = 252/840 - Subtract the two like fractions:
420/840 - 252/840 = 420 - 252/840 = 168/840 - After reducing the fraction, the answer is 1/5
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