Subtract 15/40 from 21/84
21/84 - 15/40 is -1/8.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 84 and 40 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 84 × 10 = 840,
21/84 = 21 × 10/84 × 10 = 210/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
15/40 = 15 × 21/40 × 21 = 315/840 - Subtract the two like fractions:
210/840 - 315/840 = 210 - 315/840 = -105/840 - After reducing the fraction, the answer is -1/8
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/84-15/40 21/84-30/40 21/84-15/80 63/84-15/40 21/84-45/40 21/84-75/40