

Adding like fractions  Adding
unlike fractions 
We call fractions which have the same denominator like fractions. To add like fractions we just need to add the numerators. Example
1: 1/4 + 3/4 = 1
Although
we have shown the setting out above, we really don't need to do any working
out to solve this problem. We can easily picture an object divided into
4 equal parts, quarters, and then add 3 quarters to 1 quarter.
Adding fractions with different denominators is not that much harder than adding like fractions. We just need to change the unlike fractions into like fractions. Example
2: Adding
unlike fractions using a model, 1/2 + 1/3 = 5/6 The model of the cake enabled us to picture this problem. We could also solve the problem without a model, as set out below:
Example 3: adding unlike fractions with unrelated denominators, 2/7 + 3/4 = 1 1/28 Example 4: adding unlike fractions with related denominators, 1/4 + 5/6 = 1 1/12 Example 5: adding unlike fractions with unrelated denominators, 3/4 + 4/5 = 1 11/20 Example
6: adding unlike fractions with related denominators, 2/3 + 7/15 = 1 2/15 Before you solve a mathematics problem it is important to have some idea about what the answer might be. Can you estimate the answer to this problem? Example 7: 1 1/3 + 3 3/4 = ? How did you estimate the answer? Did you:
We can use two methods to accurately find the answer to this question:
We can add the whole numbers first and then add the fractional parts.
General rule for addition of fractions There is a general rule which can be used for addition of fractions. However this method is not always the most efficient method to use to add fractions. Try using the rule to solve, 1/24 + 5/12 = ? Example 8: Is there an easier way to find an answer to 1/24 + 5/12?
Remember, if the question has mixed numbers, you can add the whole numbers first and then the fractions, or, you can change the mixed numbers to improper fractions and then add these fractions. In any case you must always find a common denominator before you add fractions. Perform the following additions. Express your answer using the lowest possible denominator.
To view the quiz answers, click here.


© University of Melbourne 2003 