Subtract 18/40 from 7/81
7/81 - 18/40 is -589/1620.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 81 and 40 is 3240
Next, find the equivalent fraction of both fractional numbers with denominator 3240 - For the 1st fraction, since 81 × 40 = 3240,
7/81 = 7 × 40/81 × 40 = 280/3240 - Likewise, for the 2nd fraction, since 40 × 81 = 3240,
18/40 = 18 × 81/40 × 81 = 1458/3240 - Subtract the two like fractions:
280/3240 - 1458/3240 = 280 - 1458/3240 = -1178/3240 - After reducing the fraction, the answer is -589/1620
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 14/81-18/40 7/81-36/40 7/81-18/80 21/81-18/40 7/81-54/40 35/81-18/40 7/81-90/40 49/81-18/40