Add 20/12 and 28/21
1st number: 1 8/12, 2nd number: 1 7/21
20/12 + 28/21 is 3/1.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 12 and 21 is 84
Next, find the equivalent fraction of both fractional numbers with denominator 84 - For the 1st fraction, since 12 × 7 = 84,
20/12 = 20 × 7/12 × 7 = 140/84 - Likewise, for the 2nd fraction, since 21 × 4 = 84,
28/21 = 28 × 4/21 × 4 = 112/84 - Add the two like fractions:
140/84 + 112/84 = 140 + 112/84 = 252/84 - 252/84 simplified gives 3/1
- So, 20/12 + 28/21 = 3/1
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 40/12+28/21 20/12+56/21 20/24+28/21 20/12+28/42 60/12+28/21 20/12+84/21 20/36+28/21 20/12+28/63 20/60+28/21 20/84+28/21