Subtract 20/42 from 15/40
15/40 - 20/42 is -17/168.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 40 and 42 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 40 × 21 = 840,
15/40 = 15 × 21/40 × 21 = 315/840 - Likewise, for the 2nd fraction, since 42 × 20 = 840,
20/42 = 20 × 20/42 × 20 = 400/840 - Subtract the two like fractions:
315/840 - 400/840 = 315 - 400/840 = -85/840 - After reducing the fraction, the answer is -17/168
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 30/40-20/42 15/40-40/42 15/80-20/42 15/40-20/84 45/40-20/42 15/40-60/42 75/40-20/42