Subtract 21/42 from 7/45
7/45 - 21/42 is -31/90.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 45 and 42 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 45 × 14 = 630,
7/45 = 7 × 14/45 × 14 = 98/630 - Likewise, for the 2nd fraction, since 42 × 15 = 630,
21/42 = 21 × 15/42 × 15 = 315/630 - Subtract the two like fractions:
98/630 - 315/630 = 98 - 315/630 = -217/630 - After reducing the fraction, the answer is -31/90
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 14/45-21/42 7/90-21/42 7/45-21/84 21/45-21/42 7/45-63/42 35/45-21/42 49/45-21/42