Add 12/15 and 21/90
12/15 + 21/90 is 31/30.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 15 and 90 is 90
Next, find the equivalent fraction of both fractional numbers with denominator 90 - For the 1st fraction, since 15 × 6 = 90,
12/15 = 12 × 6/15 × 6 = 72/90 - Likewise, for the 2nd fraction, since 90 × 1 = 90,
21/90 = 21 × 1/90 × 1 = 21/90 - Add the two like fractions:
72/90 + 21/90 = 72 + 21/90 = 93/90 - 93/90 simplified gives 31/30
- So, 12/15 + 21/90 = 31/30
In mixed form: 11/30
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 24/15+21/90 12/15+42/90 12/30+21/90 36/15+21/90 12/15+63/90 12/45+21/90 60/15+21/90 12/75+21/90 84/15+21/90