Add 84/90 and 75/21, Solve 84/90 + 3 12/21 as a fraction

Add 84/90 and 75/21

1^st number: 84/90, 2^nd number: 3 12/21

84/90 + 75/21 is 473/105.

Find the least common denominator or LCM of the two denominators:
LCM of 90 and 21 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 90 × 7 = 630,
84/90 = 84 × 7/90 × 7 = 588/630
Likewise, for the 2nd fraction, since 21 × 30 = 630,
75/21 = 75 × 30/21 × 30 = 2250/630
Add the two like fractions:
588/630 + 2250/630 = 588 + 2250/630 = 2838/630
2838/630 simplified gives 473/105
So, 84/90 + 75/21 = 473/105
In mixed form: 453/105

MathStep (Works offline)

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