Adding & Subtracting Fractions with Unlike Denominators
Today we are going to learn how to add and subtract fractions with unlike denominators. First, we have some definitions to write down.
Fraction- a numerical quantity that is not a whole number. Ex: 1/4, 2/3
Denominator- the number on the bottom of the fraction. Ex: 1/4 the four is the denominator.
Numerator- the number on the top of the fraction. 1/4 the one is the numerator.
Before we can start, you have to know how to add and subtract fractions with unlike denominators.
- First, you need to find a common denominator.
- You could multiply the two denominators together or find the least common multiple.
- When you find the LCM, multiply the denominator by the number to equal the LCM. Ex: 1/4 and 2/3 the LCM is 12, so multiply 4 by 3 and 3 by 4. Then, you have your new denominator
- Secondly, you need new numerators. Whatever you multiplied the denominator by, you multiply the numerator by. Ex: 1/4 and 2/3 multiply 1 by 3 and 2 by 4
- Your whole new fractions would be: 3/12 + 8/12= 11/12
- The next step is to either; add or subtract.
- The last step, is to simplify.
Now, we are going to do some example problems.
1/5 + 2/3
3/8 + 4/7
Do these on your own.
4/5 + 7/8
2/4 + 5/7
7/9 + 3/4
Now let's try some subtraction.
4/5 - 3/4
5/6 - 4/5