Add 8/20 and 70/42, Solve 8/20 + 1 28/42 as a fraction

Add 8/20 and 70/42

1^st number: 8/20, 2^nd number: 1 28/42

8/20 + 70/42 is 31/15.

Find the least common denominator or LCM of the two denominators:
LCM of 20 and 42 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 20 × 21 = 420,
8/20 = 8 × 21/20 × 21 = 168/420
Likewise, for the 2nd fraction, since 42 × 10 = 420,
70/42 = 70 × 10/42 × 10 = 700/420
Add the two like fractions:
168/420 + 700/420 = 168 + 700/420 = 868/420
868/420 simplified gives 31/15
So, 8/20 + 70/42 = 31/15
In mixed form: 21/15

MathStep (Works offline)

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