Add 28/21 and 21/54, Solve 1 7/21 + 21/54 as a fraction

Add 28/21 and 21/54

1^st number: 1 7/21, 2^nd number: 21/54

28/21 + 21/54 is 31/18.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 54 is 378

Next, find the equivalent fraction of both fractional numbers with denominator 378
For the 1st fraction, since 21 × 18 = 378,
28/21 = 28 × 18/21 × 18 = 504/378
Likewise, for the 2nd fraction, since 54 × 7 = 378,
21/54 = 21 × 7/54 × 7 = 147/378
Add the two like fractions:
504/378 + 147/378 = 504 + 147/378 = 651/378
651/378 simplified gives 31/18
So, 28/21 + 21/54 = 31/18
In mixed form: 113/18

MathStep (Works offline)

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