Add 81/30 and 63/42, Solve 2 21/30 + 1 21/42 as a fraction

Add 81/30 and 63/42

1^st number: 2 21/30, 2^nd number: 1 21/42

81/30 + 63/42 is 21/5.

Find the least common denominator or LCM of the two denominators:
LCM of 30 and 42 is 210

Next, find the equivalent fraction of both fractional numbers with denominator 210
For the 1st fraction, since 30 × 7 = 210,
81/30 = 81 × 7/30 × 7 = 567/210
Likewise, for the 2nd fraction, since 42 × 5 = 210,
63/42 = 63 × 5/42 × 5 = 315/210
Add the two like fractions:
567/210 + 315/210 = 567 + 315/210 = 882/210
882/210 simplified gives 21/5
So, 81/30 + 63/42 = 21/5
In mixed form: 41/5

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad