Add 15/21 and 21/18
1st number: 15/21, 2nd number: 1 3/18
15/21 + 21/18 is 79/42.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 18 is 126
Next, find the equivalent fraction of both fractional numbers with denominator 126 - For the 1st fraction, since 21 × 6 = 126,
15/21 = 15 × 6/21 × 6 = 90/126 - Likewise, for the 2nd fraction, since 18 × 7 = 126,
21/18 = 21 × 7/18 × 7 = 147/126 - Add the two like fractions:
90/126 + 147/126 = 90 + 147/126 = 237/126 - 237/126 simplified gives 79/42
- So, 15/21 + 21/18 = 79/42
In mixed form: 137/42
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 30/21+21/18 15/21+42/18 15/42+21/18 15/21+21/36 45/21+21/18 15/21+63/18 15/63+21/18 15/21+21/54 75/21+21/18 15/21+21/90