Add 21/12 and 45/40, Solve 1 9/12 + 1 5/40 as a fraction

Add 21/12 and 45/40

1^st number: 1 9/12, 2^nd number: 1 5/40

21/12 + 45/40 is 23/8.

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

Next, find the equivalent fraction of both fractional numbers with denominator 120
For the 1st fraction, since 12 × 10 = 120,
21/12 = 21 × 10/12 × 10 = 210/120
Likewise, for the 2nd fraction, since 40 × 3 = 120,
45/40 = 45 × 3/40 × 3 = 135/120
Add the two like fractions:
210/120 + 135/120 = 210 + 135/120 = 345/120
345/120 simplified gives 23/8
So, 21/12 + 45/40 = 23/8
In mixed form: 27/8

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