Subtract 42/72 from 21/45
21/45 - 42/72 is -7/60.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 45 and 72 is 360
Next, find the equivalent fraction of both fractional numbers with denominator 360 - For the 1st fraction, since 45 × 8 = 360,
21/45 = 21 × 8/45 × 8 = 168/360 - Likewise, for the 2nd fraction, since 72 × 5 = 360,
42/72 = 42 × 5/72 × 5 = 210/360 - Subtract the two like fractions:
168/360 - 210/360 = 168 - 210/360 = -42/360 - After reducing the fraction, the answer is -7/60
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/45-42/72 21/45-84/72 21/90-42/72 63/45-42/72