Add 21/20 and 9/84, Solve 1 1/20 + 9/84 as a fraction

Add 21/20 and 9/84

1^st number: 1 1/20, 2^nd number: 9/84

21/20 + 9/84 is 81/70.

Find the least common denominator or LCM of the two denominators:
LCM of 20 and 84 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 20 × 21 = 420,
21/20 = 21 × 21/20 × 21 = 441/420
Likewise, for the 2nd fraction, since 84 × 5 = 420,
9/84 = 9 × 5/84 × 5 = 45/420
Add the two like fractions:
441/420 + 45/420 = 441 + 45/420 = 486/420
486/420 simplified gives 81/70
So, 21/20 + 9/84 = 81/70
In mixed form: 111/70

MathStep (Works offline)

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