Add 21/42 and 18/20
21/42 + 18/20 is 7/5.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 20 is 420
Next, find the equivalent fraction of both fractional numbers with denominator 420 - For the 1st fraction, since 42 × 10 = 420,
21/42 = 21 × 10/42 × 10 = 210/420 - Likewise, for the 2nd fraction, since 20 × 21 = 420,
18/20 = 18 × 21/20 × 21 = 378/420 - Add the two like fractions:
210/420 + 378/420 = 210 + 378/420 = 588/420 - 588/420 simplified gives 7/5
- So, 21/42 + 18/20 = 7/5
In mixed form: 12/5
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42+36/20 21/84+18/20 21/42+18/40 63/42+18/20 21/42+54/20 21/42+18/60 21/42+90/20