Subtract 9/10 from 21/84
21/84 - 9/10 is -13/20.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 84 and 10 is 420
Next, find the equivalent fraction of both fractional numbers with denominator 420 - For the 1st fraction, since 84 × 5 = 420,
21/84 = 21 × 5/84 × 5 = 105/420 - Likewise, for the 2nd fraction, since 10 × 42 = 420,
9/10 = 9 × 42/10 × 42 = 378/420 - Subtract the two like fractions:
105/420 - 378/420 = 105 - 378/420 = -273/420 - After reducing the fraction, the answer is -13/20
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/84-9/10 21/84-18/10 21/84-9/20 63/84-9/10 21/84-27/10 21/84-9/30 21/84-45/10 21/84-9/50 21/84-63/10 21/84-9/70