Compare 18/21 and 81/20, Which fraction is greater?

Compare 18/21 and 81/20

1^st number: 18/21, 2^nd number: 4 1/20

18/21 is smaller than 81/20

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 20 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 21 × 20 = 420,
18/21 = 18 × 20/21 × 20 = 360/420
Likewise, for the 2nd fraction, since 20 × 21 = 420,
81/20 = 81 × 21/20 × 21 = 1701/420
Since the denominators are now the same, the fraction with the bigger numerator is the greater fraction
360/420 < 1701/420 or 18/21 < 81/20

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