Add 15/4 and 7/21, Solve 3 3/4 + 7/21 as a fraction

Add 15/4 and 7/21

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

15/4 + 7/21 is 49/12.

Find the least common denominator or LCM of the two denominators:
LCM of 4 and 21 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 4 × 21 = 84,
15/4 = 15 × 21/4 × 21 = 315/84
Likewise, for the 2nd fraction, since 21 × 4 = 84,
7/21 = 7 × 4/21 × 4 = 28/84
Add the two like fractions:
315/84 + 28/84 = 315 + 28/84 = 343/84
343/84 simplified gives 49/12
So, 15/4 + 7/21 = 49/12
In mixed form: 41/12

MathStep (Works offline)

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