Subtract 20/40 from 12/42
12/42 - 20/40 is -3/14.
Steps for subtracting 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,
12/42 = 12 × 20/42 × 20 = 240/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
20/40 = 20 × 21/40 × 21 = 420/840 - Subtract the two like fractions:
240/840 - 420/840 = 240 - 420/840 = -180/840 - After reducing the fraction, the answer is -3/14
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 24/42-20/40 12/84-20/40 12/42-20/80 36/42-20/40 12/42-60/40 60/42-20/40 84/42-20/40