How to Add Fractions with Different Denominators

Introduction

Adding fractions with different denominators can be confusing...unless you have common denominators. You can always change the denominators so that they are the same and that way they are also easy to add. 

The main thing that you have to do when changing different denominators in to common denominators is that you have to find the LCM of the two denominators. That is pretty much the key to this topic!

Add Fractions with Different Denominators

Let's say that we have 4/18+6/12. 

First, you have to list the common multiples of 12 and 18:

12= 12,24,36

18= 18,36

The LCM of 12 and 18 is 36.

Next, we'll have to figure out the numerators by finding what number we multiplied the original numerator by to get the new numerator of 36.

4/18= 8/36 because we multiplied by 2.

6/12= 18/36 because we multiplied by 3.

That means that we now have 8/36+18+36 which equals 26/36. Remember to simplify: 26/36=13/18.

 Sheet 1 Practice Problems on Adding Fractions