Subtract 28/40 from 21/90
21/90 - 28/40 is -7/15.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 90 and 40 is 360
Next, find the equivalent fraction of both fractional numbers with denominator 360 - For the 1st fraction, since 90 × 4 = 360,
21/90 = 21 × 4/90 × 4 = 84/360 - Likewise, for the 2nd fraction, since 40 × 9 = 360,
28/40 = 28 × 9/40 × 9 = 252/360 - Subtract the two like fractions:
84/360 - 252/360 = 84 - 252/360 = -168/360 - After reducing the fraction, the answer is -7/15
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/90-28/40 21/90-56/40 21/90-28/80 63/90-28/40 21/90-84/40