Subtract 21/40 from 18/42
18/42 - 21/40 is -27/280.
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,
18/42 = 18 × 20/42 × 20 = 360/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
21/40 = 21 × 21/40 × 21 = 441/840 - Subtract the two like fractions:
360/840 - 441/840 = 360 - 441/840 = -81/840 - After reducing the fraction, the answer is -27/280
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