Subtract 21/42 from 18/90
18/90 - 21/42 is -3/10.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 90 and 42 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 90 × 7 = 630,
18/90 = 18 × 7/90 × 7 = 126/630 - Likewise, for the 2nd fraction, since 42 × 15 = 630,
21/42 = 21 × 15/42 × 15 = 315/630 - Subtract the two like fractions:
126/630 - 315/630 = 126 - 315/630 = -189/630 - After reducing the fraction, the answer is -3/10
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