Add 15/42 and 45/12, Solve 15/42 + 3 9/12 as a fraction

Add 15/42 and 45/12

1^st number: 15/42, 2^nd number: 3 9/12

15/42 + 45/12 is 115/28.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 12 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 42 × 2 = 84,
15/42 = 15 × 2/42 × 2 = 30/84
Likewise, for the 2nd fraction, since 12 × 7 = 84,
45/12 = 45 × 7/12 × 7 = 315/84
Add the two like fractions:
30/84 + 315/84 = 30 + 315/84 = 345/84
345/84 simplified gives 115/28
So, 15/42 + 45/12 = 115/28
In mixed form: 43/28

MathStep (Works offline)

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