Add 4/5 and 70/21, Solve 4/5 + 3 7/21 as a fraction

Add 4/5 and 70/21

1^st number: 4/5, 2^nd number: 3 7/21

4/5 + 70/21 is 62/15.

Find the least common denominator or LCM of the two denominators:
LCM of 5 and 21 is 105

Next, find the equivalent fraction of both fractional numbers with denominator 105
For the 1st fraction, since 5 × 21 = 105,
4/5 = 4 × 21/5 × 21 = 84/105
Likewise, for the 2nd fraction, since 21 × 5 = 105,
70/21 = 70 × 5/21 × 5 = 350/105
Add the two like fractions:
84/105 + 350/105 = 84 + 350/105 = 434/105
434/105 simplified gives 62/15
So, 4/5 + 70/21 = 62/15
In mixed form: 42/15

MathStep (Works offline)

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