Add 21/42 and 42/45, Solve 21/42 + 42/45 as a fraction

Add 21/42 and 42/45

21/42 + 42/45 is 43/30.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 45 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 42 × 15 = 630,
21/42 = 21 × 15/42 × 15 = 315/630
Likewise, for the 2nd fraction, since 45 × 14 = 630,
42/45 = 42 × 14/45 × 14 = 588/630
Add the two like fractions:
315/630 + 588/630 = 315 + 588/630 = 903/630
903/630 simplified gives 43/30
So, 21/42 + 42/45 = 43/30
In mixed form: 113/30

MathStep (Works offline)

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