Subtract 8/20 from 21/81
21/81 - 8/20 is -19/135.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 81 and 20 is 1620
Next, find the equivalent fraction of both fractional numbers with denominator 1620 - For the 1st fraction, since 81 × 20 = 1620,
21/81 = 21 × 20/81 × 20 = 420/1620 - Likewise, for the 2nd fraction, since 20 × 81 = 1620,
8/20 = 8 × 81/20 × 81 = 648/1620 - Subtract the two like fractions:
420/1620 - 648/1620 = 420 - 648/1620 = -228/1620 - After reducing the fraction, the answer is -19/135
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 42/81-8/20 21/81-16/20 21/81-8/40 63/81-8/20 21/81-24/20 21/81-8/60 21/81-40/20 21/81-56/20