Subtract 21/40 from 18/72
18/72 - 21/40 is -11/40.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 72 and 40 is 360
Next, find the equivalent fraction of both fractional numbers with denominator 360 - For the 1st fraction, since 72 × 5 = 360,
18/72 = 18 × 5/72 × 5 = 90/360 - Likewise, for the 2nd fraction, since 40 × 9 = 360,
21/40 = 21 × 9/40 × 9 = 189/360 - Subtract the two like fractions:
90/360 - 189/360 = 90 - 189/360 = -99/360 - After reducing the fraction, the answer is -11/40
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/72-21/40 18/72-42/40 18/72-21/80 54/72-21/40 18/72-63/40 90/72-21/40