Subtract 15/81 from 3/21, Solve 3/21

Subtract 15/81 from 3/21

3/21 - 15/81 is -8/189.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 81 is 567

Next, find the equivalent fraction of both fractional numbers with denominator 567
For the 1st fraction, since 21 × 27 = 567,
3/21 = 3 × 27/21 × 27 = 81/567
Likewise, for the 2nd fraction, since 81 × 7 = 567,
15/81 = 15 × 7/81 × 7 = 105/567
Subtract the two like fractions:
81/567 - 105/567 = 81 - 105/567 = -24/567
After reducing the fraction, the answer is -8/189

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad