Subtract 42/90 from 8/21
8/21 - 42/90 is -3/35.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 90 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 21 × 30 = 630,
8/21 = 8 × 30/21 × 30 = 240/630 - Likewise, for the 2nd fraction, since 90 × 7 = 630,
42/90 = 42 × 7/90 × 7 = 294/630 - Subtract the two like fractions:
240/630 - 294/630 = 240 - 294/630 = -54/630 - After reducing the fraction, the answer is -3/35
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 16/21-42/90 8/21-84/90 8/42-42/90 24/21-42/90 8/63-42/90 40/21-42/90 56/21-42/90