Add 21/42 and 45/12, Solve 21/42 + 3 9/12 as a fraction

Add 21/42 and 45/12

1^st number: 21/42, 2^nd number: 3 9/12

21/42 + 45/12 is 17/4.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 12 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 42 × 2 = 84,
21/42 = 21 × 2/42 × 2 = 42/84
Likewise, for the 2nd fraction, since 12 × 7 = 84,
45/12 = 45 × 7/12 × 7 = 315/84
Add the two like fractions:
42/84 + 315/84 = 42 + 315/84 = 357/84
357/84 simplified gives 17/4
So, 21/42 + 45/12 = 17/4
In mixed form: 41/4

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