Add 21/42 and 45/40
1st number: 21/42, 2nd number: 1 5/40
21/42 + 45/40 is 13/8.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 40 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 42 × 20 = 840,
21/42 = 21 × 20/42 × 20 = 420/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
45/40 = 45 × 21/40 × 21 = 945/840 - Add the two like fractions:
420/840 + 945/840 = 420 + 945/840 = 1365/840 - 1365/840 simplified gives 13/8
- So, 21/42 + 45/40 = 13/8
In mixed form: 15/8
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42+90/40 21/84+45/40 21/42+45/80 63/42+45/40