Add 12/18 and 15/21, Solve 12/18 + 15/21 as a fraction

Add 12/18 and 15/21

12/18 + 15/21 is 29/21.

Find the least common denominator or LCM of the two denominators:
LCM of 18 and 21 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 18 × 7 = 126,
12/18 = 12 × 7/18 × 7 = 84/126
Likewise, for the 2nd fraction, since 21 × 6 = 126,
15/21 = 15 × 6/21 × 6 = 90/126
Add the two like fractions:
84/126 + 90/126 = 84 + 90/126 = 174/126
174/126 simplified gives 29/21
So, 12/18 + 15/21 = 29/21
In mixed form: 18/21

MathStep (Works offline)

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