Add 72/21 and 20/80, Solve 3 9/21 + 20/80 as a fraction

Add 72/21 and 20/80

1^st number: 3 9/21, 2^nd number: 20/80

72/21 + 20/80 is 103/28.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 80 is 1680

Next, find the equivalent fraction of both fractional numbers with denominator 1680
For the 1st fraction, since 21 × 80 = 1680,
72/21 = 72 × 80/21 × 80 = 5760/1680
Likewise, for the 2nd fraction, since 80 × 21 = 1680,
20/80 = 20 × 21/80 × 21 = 420/1680
Add the two like fractions:
5760/1680 + 420/1680 = 5760 + 420/1680 = 6180/1680
6180/1680 simplified gives 103/28
So, 72/21 + 20/80 = 103/28
In mixed form: 319/28

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