Subtract 30/21 from 42/30, Solve 1 12/30

Subtract 30/21 from 42/30

1^st number: 1 12/30, 2^nd number: 1 9/21

42/30 - 30/21 is -1/35.

Find the least common denominator or LCM of the two denominators:
LCM of 30 and 21 is 210

Next, find the equivalent fraction of both fractional numbers with denominator 210
For the 1st fraction, since 30 × 7 = 210,
42/30 = 42 × 7/30 × 7 = 294/210
Likewise, for the 2nd fraction, since 21 × 10 = 210,
30/21 = 30 × 10/21 × 10 = 300/210
Subtract the two like fractions:
294/210 - 300/210 = 294 - 300/210 = -6/210
After reducing the fraction, the answer is -1/35

MathStep (Works offline)

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