Add 72/21 and 84/20, Solve 3 9/21 + 4 4/20 as a fraction

Add 72/21 and 84/20

1^st number: 3 9/21, 2^nd number: 4 4/20

72/21 + 84/20 is 267/35.

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,
72/21 = 72 × 20/21 × 20 = 1440/420
Likewise, for the 2nd fraction, since 20 × 21 = 420,
84/20 = 84 × 21/20 × 21 = 1764/420
Add the two like fractions:
1440/420 + 1764/420 = 1440 + 1764/420 = 3204/420
3204/420 simplified gives 267/35
So, 72/21 + 84/20 = 267/35
In mixed form: 722/35

MathStep (Works offline)

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