Subtract 15/40 from 21/84, Solve 21/84

Subtract 15/40 from 21/84

21/84 - 15/40 is -1/8.

Find the least common denominator or LCM of the two denominators:
LCM of 84 and 40 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 84 × 10 = 840,
21/84 = 21 × 10/84 × 10 = 210/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
15/40 = 15 × 21/40 × 21 = 315/840
Subtract the two like fractions:
210/840 - 315/840 = 210 - 315/840 = -105/840
After reducing the fraction, the answer is -1/8

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