Add 21/40 and 45/12, Solve 21/40 + 3 9/12 as a fraction

Add 21/40 and 45/12

1^st number: 21/40, 2^nd number: 3 9/12

21/40 + 45/12 is 171/40.

Find the least common denominator or LCM of the two denominators:
LCM of 40 and 12 is 120

Next, find the equivalent fraction of both fractional numbers with denominator 120
For the 1st fraction, since 40 × 3 = 120,
21/40 = 21 × 3/40 × 3 = 63/120
Likewise, for the 2nd fraction, since 12 × 10 = 120,
45/12 = 45 × 10/12 × 10 = 450/120
Add the two like fractions:
63/120 + 450/120 = 63 + 450/120 = 513/120
513/120 simplified gives 171/40
So, 21/40 + 45/12 = 171/40
In mixed form: 411/40

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