Add 21/40 and 9/15
21/40 + 9/15 is 9/8.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 40 and 15 is 120
Next, find the equivalent fraction of both fractional numbers with denominator 120 - For the 1st fraction, since 40 × 3 = 120,
21/40 = 21 × 3/40 × 3 = 63/120 - Likewise, for the 2nd fraction, since 15 × 8 = 120,
9/15 = 9 × 8/15 × 8 = 72/120 - Add the two like fractions:
63/120 + 72/120 = 63 + 72/120 = 135/120 - 135/120 simplified gives 9/8
- So, 21/40 + 9/15 = 9/8
In mixed form: 11/8
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/40+9/15 21/40+18/15 21/80+9/15 21/40+9/30 63/40+9/15 21/40+27/15 21/40+9/45 21/40+45/15 21/40+9/75 21/40+63/15