Compare 21/49 and 42/80, Which fraction is greater?

Compare 21/49 and 42/80

21/49 is smaller than 42/80

Find the least common denominator or LCM of the two denominators:
LCM of 49 and 80 is 3920

Next, find the equivalent fraction of both fractional numbers with denominator 3920
For the 1st fraction, since 49 × 80 = 3920,
21/49 = 21 × 80/49 × 80 = 1680/3920
Likewise, for the 2nd fraction, since 80 × 49 = 3920,
42/80 = 42 × 49/80 × 49 = 2058/3920
Since the denominators are now the same, the fraction with the bigger numerator is the greater fraction
1680/3920 < 2058/3920 or 21/49 < 42/80

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