Adding Mixed Numbers with Different Denominators

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You can add only fractions together that have the same dennominator, so you must first change each of the two fractions to a common denominator.

Example 1 Suppose you have two mixed numbers 1 1/3 and 3 1/4 to be added together

1	1		3	1
	---	+		---	=		---
	3			4

First you must find common denominators.

Select the denominator of the second fraction (4) and multiply the numerator and denominator of the first fraction (1/3) by that number:

1		4		4
---	x	---	=	---
3		4		12

Select the denominator of the first fraction (3) and multiply the numerator and denominator of the second fraction (1/4) by that number:

1		3		3
---	x	---	=	---
4		3		12

These two fractions (4/12 and 3/12) have common denominators.

Add the two new fractions together. Do not add the denominators together.

4		3		7
---	+	---	=	---
12		12		12

So your answer will be 4 and 7/12.

1	4		3	3		4	7
	---	+		---	=		---
	12			12			12