Subtract 18/7 from 21/81
1st number: 21/81, 2nd number: 2 4/7
21/81 - 18/7 is -437/189.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 81 and 7 is 567
Next, find the equivalent fraction of both fractional numbers with denominator 567 - For the 1st fraction, since 81 × 7 = 567,
21/81 = 21 × 7/81 × 7 = 147/567 - Likewise, for the 2nd fraction, since 7 × 81 = 567,
18/7 = 18 × 81/7 × 81 = 1458/567 - Subtract the two like fractions:
147/567 - 1458/567 = 147 - 1458/567 = -1311/567 - After reducing the fraction, the answer is -437/189
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/81-18/7 21/81-36/7 21/81-18/14 63/81-18/7 21/81-54/7 21/81-18/21 21/81-90/7 21/81-18/35 21/81-18/49