Subtract 1/8 from 21/81, Solve 21/81

Subtract 1/8 from 21/81

21/81 - 1/8 is 29/216.

Find the least common denominator or LCM of the two denominators:
LCM of 81 and 8 is 648

Next, find the equivalent fraction of both fractional numbers with denominator 648
For the 1st fraction, since 81 × 8 = 648,
21/81 = 21 × 8/81 × 8 = 168/648
Likewise, for the 2nd fraction, since 8 × 81 = 648,
1/8 = 1 × 81/8 × 81 = 81/648
Subtract the two like fractions:
168/648 - 81/648 = 168 - 81/648 = 87/648
After reducing the fraction, the answer is 29/216

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad