Subtract 80/21 from 70/40, Solve 1 30/40

Subtract 80/21 from 70/40

1^st number: 1 30/40, 2^nd number: 3 17/21

70/40 - 80/21 is -173/84.

Find the least common denominator or LCM of the two denominators:
LCM of 40 and 21 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 40 × 21 = 840,
70/40 = 70 × 21/40 × 21 = 1470/840
Likewise, for the 2nd fraction, since 21 × 40 = 840,
80/21 = 80 × 40/21 × 40 = 3200/840
Subtract the two like fractions:
1470/840 - 3200/840 = 1470 - 3200/840 = -1730/840
After reducing the fraction, the answer is -173/84

MathStep (Works offline)

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