LESSON: Adding and Subtracting Fractions with Unlike Denominators

READ: Subtract Fractions with Different Denominators

Subtract Fractions with Different Denominators

Just as we can add fractions with different denominators by renaming them with the lowest common denominator, we can also subtract fractions with different denominators by doing the same thing.

First, remember that to subtract two fractions with different denominators, we have to make them fractions with the same denominator. We do this by finding the least common multiple and then we rename each fraction as an equivalent fraction with that least common multiple as the lowest common denominator.

Example

$\frac{6}{8} - \frac{1}{4} = \underline{\;\;\;\;\;\;\;\;\;}$

First, find the least common multiple of 4 and 8. It is 8.

Next, rename each fraction in terms of eighths. Remember that renaming is another way of saying that we create an equivalent fraction in terms of eighths.

$\frac{6}{8}$ is already in terms of eighths. We leave it alone.

$\frac{1}{4} = \frac{2}{8}$

Now we can rewrite the problem and find the difference.

$\frac{6}{8} - \frac{2}{8} = \frac{4}{8}$

We can simplify four-eighths by dividing the numerator and the denominator by the GCF. The GCF is 4.

$\frac{4 \div 4}{8 \div 4} = \frac{1}{2}$