Subtract 42/15 from 21/84
1st number: 21/84, 2nd number: 2 12/15
21/84 - 42/15 is -51/20.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 84 and 15 is 420
Next, find the equivalent fraction of both fractional numbers with denominator 420 - For the 1st fraction, since 84 × 5 = 420,
21/84 = 21 × 5/84 × 5 = 105/420 - Likewise, for the 2nd fraction, since 15 × 28 = 420,
42/15 = 42 × 28/15 × 28 = 1176/420 - Subtract the two like fractions:
105/420 - 1176/420 = 105 - 1176/420 = -1071/420 - After reducing the fraction, the answer is -51/20
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/84-42/15 21/84-84/15 21/84-42/30 63/84-42/15 21/84-42/45 21/84-42/75