Subtract 98/90 from 81/21, Solve 3 18/21

Subtract 98/90 from 81/21

1^st number: 3 18/21, 2^nd number: 1 8/90

81/21 - 98/90 is 872/315.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 90 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 21 × 30 = 630,
81/21 = 81 × 30/21 × 30 = 2430/630
Likewise, for the 2nd fraction, since 90 × 7 = 630,
98/90 = 98 × 7/90 × 7 = 686/630
Subtract the two like fractions:
2430/630 - 686/630 = 2430 - 686/630 = 1744/630
After reducing the fraction, the answer is 872/315
In mixed form: 2242/315

MathStep (Works offline)

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