Subtract 81/21 from 12/40
1st number: 12/40, 2nd number: 3 18/21
12/40 - 81/21 is -249/70.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 40 and 21 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 40 × 21 = 840,
12/40 = 12 × 21/40 × 21 = 252/840 - Likewise, for the 2nd fraction, since 21 × 40 = 840,
81/21 = 81 × 40/21 × 40 = 3240/840 - Subtract the two like fractions:
252/840 - 3240/840 = 252 - 3240/840 = -2988/840 - After reducing the fraction, the answer is -249/70
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 24/40-81/21 12/80-81/21 12/40-81/42 36/40-81/21 12/40-81/63 60/40-81/21 84/40-81/21