Subtract 90/72 from 81/70, Solve 1 11/70

Subtract 90/72 from 81/70

1^st number: 1 11/70, 2^nd number: 1 18/72

81/70 - 90/72 is -13/140.

Find the least common denominator or LCM of the two denominators:
LCM of 70 and 72 is 2520

Next, find the equivalent fraction of both fractional numbers with denominator 2520
For the 1st fraction, since 70 × 36 = 2520,
81/70 = 81 × 36/70 × 36 = 2916/2520
Likewise, for the 2nd fraction, since 72 × 35 = 2520,
90/72 = 90 × 35/72 × 35 = 3150/2520
Subtract the two like fractions:
2916/2520 - 3150/2520 = 2916 - 3150/2520 = -234/2520
After reducing the fraction, the answer is -13/140

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