Subtract 20/12 from 42/81
1st number: 42/81, 2nd number: 1 8/12
42/81 - 20/12 is -31/27.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 81 and 12 is 324
Next, find the equivalent fraction of both fractional numbers with denominator 324 - For the 1st fraction, since 81 × 4 = 324,
42/81 = 42 × 4/81 × 4 = 168/324 - Likewise, for the 2nd fraction, since 12 × 27 = 324,
20/12 = 20 × 27/12 × 27 = 540/324 - Subtract the two like fractions:
168/324 - 540/324 = 168 - 540/324 = -372/324 - After reducing the fraction, the answer is -31/27
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 84/81-20/12 42/81-40/12 42/81-20/24 42/81-60/12 42/81-20/36 42/81-20/60 42/81-20/84