Add 21/42 and 20/45
21/42 + 20/45 is 17/18.
Steps for adding fractions
- 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,
20/45 = 20 × 14/45 × 14 = 280/630 - Add the two like fractions:
315/630 + 280/630 = 315 + 280/630 = 595/630 - 595/630 simplified gives 17/18
- So, 21/42 + 20/45 = 17/18
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42+40/45 21/84+20/45 21/42+20/90 63/42+20/45 21/42+60/45