Subtract 3/27 from 21/42, Solve 21/42

Subtract 3/27 from 21/42

21/42 - 3/27 is 7/18.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 27 is 378

Next, find the equivalent fraction of both fractional numbers with denominator 378
For the 1st fraction, since 42 × 9 = 378,
21/42 = 21 × 9/42 × 9 = 189/378
Likewise, for the 2nd fraction, since 27 × 14 = 378,
3/27 = 3 × 14/27 × 14 = 42/378
Subtract the two like fractions:
189/378 - 42/378 = 189 - 42/378 = 147/378
After reducing the fraction, the answer is 7/18

MathStep (Works offline)

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