4.7+Adding+and+Subtracting+Unlike+Fractions

Section 4.7 - Adding and Subtracting Unlike Fractions
For perhaps the 75th time now, I'll remind you that you can't add or subtract unlike terms, or unlike fractions (different denominators). However, whereas unlike terms are stuck that way, unlike fractions can be turned into like fractions so that you can add or subtract them. This is accomplished using the techniques you learned in the section on equivalent fractions - reducing by dividing by a fraction equal to 1, or building up by multiplying by a fraction equal to 1.



You are looking for a common denominator. In the example above, we found that one of the fractions had to be built up so that the denominator was the same as the other. Sometimes you can reduce to make them the same. Sometimes you have to find an equivalent fraction for both in order to get a common denominator.



media type="custom" key="8325486"

media type="custom" key="8325590"


 * Unlike Fractions with Variables**

Having a variable in the numerator is just like it was in the last section, but when the variable is in the denominator, as in the example below, it gets a bit trickier. If you look at the denominators of 3 and g below, they are both factors of 3g, so that would be the logical common denominator. The trick, then, is to multiply both fractions by the right thing to get to that denominator.




 * Chapter Four Practice Problems**

**Where to from here?**
4.1 Greatest Common Factor 4.2 What is a Fraction? 4.3 Equivalent Fractions 4.4 Multiplying Fractions 4.5 Dividing Fractions 4.6 Adding and Subtracting Like Fractions 4.7 Adding and Subtracting Unlike Fractions 4.8 Fraction Coefficients 4.9 Solving for X with Fractions Chapter Four Review Chapter Four Homework