Subtract 21/8 from 21/42
1st number: 21/42, 2nd number: 2 5/8
21/42 - 21/8 is -17/8.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 8 is 168
Next, find the equivalent fraction of both fractional numbers with denominator 168 - For the 1st fraction, since 42 × 4 = 168,
21/42 = 21 × 4/42 × 4 = 84/168 - Likewise, for the 2nd fraction, since 8 × 21 = 168,
21/8 = 21 × 21/8 × 21 = 441/168 - Subtract the two like fractions:
84/168 - 441/168 = 84 - 441/168 = -357/168 - After reducing the fraction, the answer is -17/8
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42-42/8 21/84-21/8 21/42-21/16 63/42-21/8 21/42-63/8 21/42-21/24 21/42-21/40 21/42-21/56