Subtract 18/21 from 7/40
7/40 - 18/21 is -191/280.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 40 and 21 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 40 × 21 = 840,
7/40 = 7 × 21/40 × 21 = 147/840 - Likewise, for the 2nd fraction, since 21 × 40 = 840,
18/21 = 18 × 40/21 × 40 = 720/840 - Subtract the two like fractions:
147/840 - 720/840 = 147 - 720/840 = -573/840 - After reducing the fraction, the answer is -191/280
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