Subtract 63/72 from 21/42
21/42 - 63/72 is -3/8.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 72 is 504
Next, find the equivalent fraction of both fractional numbers with denominator 504 - For the 1st fraction, since 42 × 12 = 504,
21/42 = 21 × 12/42 × 12 = 252/504 - Likewise, for the 2nd fraction, since 72 × 7 = 504,
63/72 = 63 × 7/72 × 7 = 441/504 - Subtract the two like fractions:
252/504 - 441/504 = 252 - 441/504 = -189/504 - After reducing the fraction, the answer is -3/8
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/84-63/72 63/42-63/72