Add 15/30 and 20/21
15/30 + 20/21 is 61/42.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 30 and 21 is 210
Next, find the equivalent fraction of both fractional numbers with denominator 210 - For the 1st fraction, since 30 × 7 = 210,
15/30 = 15 × 7/30 × 7 = 105/210 - Likewise, for the 2nd fraction, since 21 × 10 = 210,
20/21 = 20 × 10/21 × 10 = 200/210 - Add the two like fractions:
105/210 + 200/210 = 105 + 200/210 = 305/210 - 305/210 simplified gives 61/42
- So, 15/30 + 20/21 = 61/42
In mixed form: 119/42
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 15/30+40/21 15/60+20/21 15/30+20/42 45/30+20/21 15/30+60/21 15/90+20/21 15/30+20/63 75/30+20/21