Add 21/18 and 20/21
1st number: 1 3/18, 2nd number: 20/21
21/18 + 20/21 is 89/42.
Steps for adding fractions
- 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,
21/18 = 21 × 7/18 × 7 = 147/126 - Likewise, for the 2nd fraction, since 21 × 6 = 126,
20/21 = 20 × 6/21 × 6 = 120/126 - Add the two like fractions:
147/126 + 120/126 = 147 + 120/126 = 267/126 - 267/126 simplified gives 89/42
- So, 21/18 + 20/21 = 89/42
In mixed form: 25/42
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/18+20/21 21/18+40/21 21/36+20/21 21/18+20/42 63/18+20/21 21/18+60/21 21/54+20/21 21/18+20/63 21/90+20/21