Subtract 81/7 from 21/45, Solve 21/45

Subtract 81/7 from 21/45

1^st number: 21/45, 2^nd number: 11 4/7

21/45 - 81/7 is -1166/105.

Find the least common denominator or LCM of the two denominators:
LCM of 45 and 7 is 315

Next, find the equivalent fraction of both fractional numbers with denominator 315
For the 1st fraction, since 45 × 7 = 315,
21/45 = 21 × 7/45 × 7 = 147/315
Likewise, for the 2nd fraction, since 7 × 45 = 315,
81/7 = 81 × 45/7 × 45 = 3645/315
Subtract the two like fractions:
147/315 - 3645/315 = 147 - 3645/315 = -3498/315
After reducing the fraction, the answer is -1166/105

MathStep (Works offline)

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