Add 15/45 and 10/21, Solve 15/45 + 10/21 as a fraction

Add 15/45 and 10/21

15/45 + 10/21 is 17/21.

Find the least common denominator or LCM of the two denominators:
LCM of 45 and 21 is 315

Next, find the equivalent fraction of both fractional numbers with denominator 315
For the 1st fraction, since 45 × 7 = 315,
15/45 = 15 × 7/45 × 7 = 105/315
Likewise, for the 2nd fraction, since 21 × 15 = 315,
10/21 = 10 × 15/21 × 15 = 150/315
Add the two like fractions:
105/315 + 150/315 = 105 + 150/315 = 255/315
255/315 simplified gives 17/21
So, 15/45 + 10/21 = 17/21

MathStep (Works offline)

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