Subtract 18/40 from 12/21
12/21 - 18/40 is 17/140.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 40 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 21 × 40 = 840,
12/21 = 12 × 40/21 × 40 = 480/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
18/40 = 18 × 21/40 × 21 = 378/840 - Subtract the two like fractions:
480/840 - 378/840 = 480 - 378/840 = 102/840 - After reducing the fraction, the answer is 17/140
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 24/21-18/40 12/21-36/40 12/42-18/40 12/21-18/80 36/21-18/40 12/21-54/40 12/63-18/40 60/21-18/40 12/21-90/40 84/21-18/40