Subtract 21/45 from 20/21, Solve 20/21

Subtract 21/45 from 20/21

20/21 - 21/45 is 17/35.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 45 is 315

Next, find the equivalent fraction of both fractional numbers with denominator 315
For the 1st fraction, since 21 × 15 = 315,
20/21 = 20 × 15/21 × 15 = 300/315
Likewise, for the 2nd fraction, since 45 × 7 = 315,
21/45 = 21 × 7/45 × 7 = 147/315
Subtract the two like fractions:
300/315 - 147/315 = 300 - 147/315 = 153/315
After reducing the fraction, the answer is 17/35

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