Subtract 12/20 from 64/21, Solve 3 1/21

Subtract 12/20 from 64/21

1^st number: 3 1/21, 2^nd number: 12/20

64/21 - 12/20 is 257/105.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 20 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 21 × 20 = 420,
64/21 = 64 × 20/21 × 20 = 1280/420
Likewise, for the 2nd fraction, since 20 × 21 = 420,
12/20 = 12 × 21/20 × 21 = 252/420
Subtract the two like fractions:
1280/420 - 252/420 = 1280 - 252/420 = 1028/420
After reducing the fraction, the answer is 257/105
In mixed form: 247/105

MathStep (Works offline)

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