Add 81/21 and 1/28, Solve 3 18/21 + 1/28 as a fraction

Add 81/21 and 1/28

1^st number: 3 18/21, 2^nd number: 1/28

81/21 + 1/28 is 109/28.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 28 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 21 × 4 = 84,
81/21 = 81 × 4/21 × 4 = 324/84
Likewise, for the 2nd fraction, since 28 × 3 = 84,
1/28 = 1 × 3/28 × 3 = 3/84
Add the two like fractions:
324/84 + 3/84 = 324 + 3/84 = 327/84
327/84 simplified gives 109/28
So, 81/21 + 1/28 = 109/28
In mixed form: 325/28

MathStep (Works offline)

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