Subtract 90/70 from 15/21
1st number: 15/21, 2nd number: 1 20/70
15/21 - 90/70 is -4/7.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 70 is 210
Next, find the equivalent fraction of both fractional numbers with denominator 210 - For the 1st fraction, since 21 × 10 = 210,
15/21 = 15 × 10/21 × 10 = 150/210 - Likewise, for the 2nd fraction, since 70 × 3 = 210,
90/70 = 90 × 3/70 × 3 = 270/210 - Subtract the two like fractions:
150/210 - 270/210 = 150 - 270/210 = -120/210 - After reducing the fraction, the answer is -4/7
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 30/21-90/70 15/42-90/70 45/21-90/70 15/63-90/70 75/21-90/70