Subtract 80/81 from 21/28
21/28 - 80/81 is -77/324.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 28 and 81 is 2268
Next, find the equivalent fraction of both fractional numbers with denominator 2268 - For the 1st fraction, since 28 × 81 = 2268,
21/28 = 21 × 81/28 × 81 = 1701/2268 - Likewise, for the 2nd fraction, since 81 × 28 = 2268,
80/81 = 80 × 28/81 × 28 = 2240/2268 - Subtract the two like fractions:
1701/2268 - 2240/2268 = 1701 - 2240/2268 = -539/2268 - After reducing the fraction, the answer is -77/324
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/28-80/81 21/56-80/81 63/28-80/81 21/84-80/81