Subtract 3/42 from 72/21, Solve 3 9/21

Subtract 3/42 from 72/21

1^st number: 3 9/21, 2^nd number: 3/42

72/21 - 3/42 is 47/14.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 42 is 42

Next, find the equivalent fraction of both fractional numbers with denominator 42
For the 1st fraction, since 21 × 2 = 42,
72/21 = 72 × 2/21 × 2 = 144/42
Likewise, for the 2nd fraction, since 42 × 1 = 42,
3/42 = 3 × 1/42 × 1 = 3/42
Subtract the two like fractions:
144/42 - 3/42 = 144 - 3/42 = 141/42
After reducing the fraction, the answer is 47/14
In mixed form: 35/14

MathStep (Works offline)

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