Subtract 81/90 from 30/42
30/42 - 81/90 is -13/70.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 90 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 42 × 15 = 630,
30/42 = 30 × 15/42 × 15 = 450/630 - Likewise, for the 2nd fraction, since 90 × 7 = 630,
81/90 = 81 × 7/90 × 7 = 567/630 - Subtract the two like fractions:
450/630 - 567/630 = 450 - 567/630 = -117/630 - After reducing the fraction, the answer is -13/70
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