Add 21/27 and 4/42, Solve 21/27 + 4/42 as a fraction

Add 21/27 and 4/42

21/27 + 4/42 is 55/63.

Find the least common denominator or LCM of the two denominators:
LCM of 27 and 42 is 378

Next, find the equivalent fraction of both fractional numbers with denominator 378
For the 1st fraction, since 27 × 14 = 378,
21/27 = 21 × 14/27 × 14 = 294/378
Likewise, for the 2nd fraction, since 42 × 9 = 378,
4/42 = 4 × 9/42 × 9 = 36/378
Add the two like fractions:
294/378 + 36/378 = 294 + 36/378 = 330/378
330/378 simplified gives 55/63
So, 21/27 + 4/42 = 55/63

MathStep (Works offline)

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