Add 27/84 and 72/21, Solve 27/84 + 3 9/21 as a fraction

Add 27/84 and 72/21

1^st number: 27/84, 2^nd number: 3 9/21

27/84 + 72/21 is 15/4.

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

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 84 × 1 = 84,
27/84 = 27 × 1/84 × 1 = 27/84
Likewise, for the 2nd fraction, since 21 × 4 = 84,
72/21 = 72 × 4/21 × 4 = 288/84
Add the two like fractions:
27/84 + 288/84 = 27 + 288/84 = 315/84
315/84 simplified gives 15/4
So, 27/84 + 72/21 = 15/4
In mixed form: 33/4

MathStep (Works offline)

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