Subtract 18/21 from 21/42
21/42 - 18/21 is -5/14.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 21 is 42
Next, find the equivalent fraction of both fractional numbers with denominator 42 - For the 1st fraction, since 42 × 1 = 42,
21/42 = 21 × 1/42 × 1 = 21/42 - Likewise, for the 2nd fraction, since 21 × 2 = 42,
18/21 = 18 × 2/21 × 2 = 36/42 - Subtract the two like fractions:
21/42 - 36/42 = 21 - 36/42 = -15/42 - After reducing the fraction, the answer is -5/14
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