Add 21/90 and 81/7, Solve 21/90 + 11 4/7 as a fraction

Add 21/90 and 81/7

1^st number: 21/90, 2^nd number: 11 4/7

21/90 + 81/7 is 2479/210.

Find the least common denominator or LCM of the two denominators:
LCM of 90 and 7 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 90 × 7 = 630,
21/90 = 21 × 7/90 × 7 = 147/630
Likewise, for the 2nd fraction, since 7 × 90 = 630,
81/7 = 81 × 90/7 × 90 = 7290/630
Add the two like fractions:
147/630 + 7290/630 = 147 + 7290/630 = 7437/630
7437/630 simplified gives 2479/210
So, 21/90 + 81/7 = 2479/210
In mixed form: 11169/210

MathStep (Works offline)

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