Subtract 21/70 from 21/90
21/90 - 21/70 is -1/15.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 90 and 70 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 90 × 7 = 630,
21/90 = 21 × 7/90 × 7 = 147/630 - Likewise, for the 2nd fraction, since 70 × 9 = 630,
21/70 = 21 × 9/70 × 9 = 189/630 - Subtract the two like fractions:
147/630 - 189/630 = 147 - 189/630 = -42/630 - After reducing the fraction, the answer is -1/15
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/90-21/70 21/90-42/70 63/90-21/70 21/90-63/70