Subtract 45/10 from 21/84, Solve 21/84

Subtract 45/10 from 21/84

1^st number: 21/84, 2^nd number: 4 5/10

21/84 - 45/10 is -17/4.

Find the least common denominator or LCM of the two denominators:
LCM of 84 and 10 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 84 × 5 = 420,
21/84 = 21 × 5/84 × 5 = 105/420
Likewise, for the 2nd fraction, since 10 × 42 = 420,
45/10 = 45 × 42/10 × 42 = 1890/420
Subtract the two like fractions:
105/420 - 1890/420 = 105 - 1890/420 = -1785/420
After reducing the fraction, the answer is -17/4

MathStep (Works offline)

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