Subtract 25/40 from 12/21, Solve 12/21

Subtract 25/40 from 12/21

12/21 - 25/40 is -3/56.

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

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 21 × 40 = 840,
12/21 = 12 × 40/21 × 40 = 480/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
25/40 = 25 × 21/40 × 21 = 525/840
Subtract the two like fractions:
480/840 - 525/840 = 480 - 525/840 = -45/840
After reducing the fraction, the answer is -3/56

MathStep (Works offline)

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