Subtract 15/42 from 7/21
7/21 - 15/42 is -1/42.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 42 is 42
Next, find the equivalent fraction of both fractional numbers with denominator 42 - For the 1st fraction, since 21 × 2 = 42,
7/21 = 7 × 2/21 × 2 = 14/42 - Likewise, for the 2nd fraction, since 42 × 1 = 42,
15/42 = 15 × 1/42 × 1 = 15/42 - Subtract the two like fractions:
14/42 - 15/42 = 14 - 15/42 = -1/42
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 14/21-15/42 7/21-30/42 7/42-15/42 7/21-15/84 7/21-45/42 7/63-15/42 35/21-15/42 7/21-75/42 49/21-15/42