Add 9/12 and 21/7, Solve 9/12 + 3 0/7 as a fraction

Add 9/12 and 21/7

1^st number: 9/12, 2^nd number: 3 0/7

9/12 + 21/7 is 15/4.

Find the least common denominator or LCM of the two denominators:
LCM of 12 and 7 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 12 × 7 = 84,
9/12 = 9 × 7/12 × 7 = 63/84
Likewise, for the 2nd fraction, since 7 × 12 = 84,
21/7 = 21 × 12/7 × 12 = 252/84
Add the two like fractions:
63/84 + 252/84 = 63 + 252/84 = 315/84
315/84 simplified gives 15/4
So, 9/12 + 21/7 = 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