Subtract 81/21 from 4/80, Solve 4/80

Subtract 81/21 from 4/80

1^st number: 4/80, 2^nd number: 3 18/21

4/80 - 81/21 is -533/140.

Find the least common denominator or LCM of the two denominators:
LCM of 80 and 21 is 1680

Next, find the equivalent fraction of both fractional numbers with denominator 1680
For the 1st fraction, since 80 × 21 = 1680,
4/80 = 4 × 21/80 × 21 = 84/1680
Likewise, for the 2nd fraction, since 21 × 80 = 1680,
81/21 = 81 × 80/21 × 80 = 6480/1680
Subtract the two like fractions:
84/1680 - 6480/1680 = 84 - 6480/1680 = -6396/1680
After reducing the fraction, the answer is -533/140

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