Subtract 4/72 from 21/42
21/42 - 4/72 is 4/9.
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,
4/72 = 4 × 7/72 × 7 = 28/504 - Subtract the two like fractions:
252/504 - 28/504 = 252 - 28/504 = 224/504 - After reducing the fraction, the answer is 4/9
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42-8/72 21/84-4/72 63/42-4/72 21/42-12/72 21/42-20/72 21/42-28/72