Add 72/90 and 42/21
1st number: 72/90, 2nd number: 2 0/21
72/90 + 42/21 is 14/5.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 90 and 21 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 90 × 7 = 630,
72/90 = 72 × 7/90 × 7 = 504/630 - Likewise, for the 2nd fraction, since 21 × 30 = 630,
42/21 = 42 × 30/21 × 30 = 1260/630 - Add the two like fractions:
504/630 + 1260/630 = 504 + 1260/630 = 1764/630 - 1764/630 simplified gives 14/5
- So, 72/90 + 42/21 = 14/5
In mixed form: 24/5
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 72/90+84/21 72/90+42/63