Subtract 7/21 from 21/72, Solve 21/72

Subtract 7/21 from 21/72

21/72 - 7/21 is -1/24.

Find the least common denominator or LCM of the two denominators:
LCM of 72 and 21 is 504

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 72 × 7 = 504,
21/72 = 21 × 7/72 × 7 = 147/504
Likewise, for the 2nd fraction, since 21 × 24 = 504,
7/21 = 7 × 24/21 × 24 = 168/504
Subtract the two like fractions:
147/504 - 168/504 = 147 - 168/504 = -21/504
After reducing the fraction, the answer is -1/24

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