Subtract 21/8 from 18/30
1st number: 18/30, 2nd number: 2 5/8
18/30 - 21/8 is -81/40.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 30 and 8 is 120
Next, find the equivalent fraction of both fractional numbers with denominator 120 - For the 1st fraction, since 30 × 4 = 120,
18/30 = 18 × 4/30 × 4 = 72/120 - Likewise, for the 2nd fraction, since 8 × 15 = 120,
21/8 = 21 × 15/8 × 15 = 315/120 - Subtract the two like fractions:
72/120 - 315/120 = 72 - 315/120 = -243/120 - After reducing the fraction, the answer is -81/40
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/30-21/8 18/30-42/8 18/60-21/8 18/30-21/16 54/30-21/8 18/30-63/8 18/90-21/8 18/30-21/24 90/30-21/8 18/30-21/40 18/30-21/56