Subtract 40/42 from 81/90
81/90 - 40/42 is -11/210.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 90 and 42 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 90 × 7 = 630,
81/90 = 81 × 7/90 × 7 = 567/630 - Likewise, for the 2nd fraction, since 42 × 15 = 630,
40/42 = 40 × 15/42 × 15 = 600/630 - Subtract the two like fractions:
567/630 - 600/630 = 567 - 600/630 = -33/630 - After reducing the fraction, the answer is -11/210
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 81/90-80/42 81/90-40/84