Subtracting Fractions Adding and Subtracting Fractions

Let’s look at a model of adding fractions. Example: First we need a fraction bar representation of each addend. We will stack these so that the shading of the second starts where the shading of the first ends. To find the answer we need to change the second to the same number of sections that the first has. 3 sections out of whole Find the total of the shaded area.

Example Find Remember: Find fraction bars to represent both addends with the same number of sections Stack these Read answer

Let’s look at subtraction… Example We are going to look at a take away model. First build only the first term. Exchange these bars for an equivalent model using eighths. Now we need to imagine taking 5/8 away and find what will be left.

Example #1 Our models show us that when adding and subtracting fractions, we need a common denominator. Once your fractions have a common denominator, you will add or subtract the numerators and keep the denominators the same.

Example #2

Example #3

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Example #5

Example #6 Felicia is making cookies for her brother’s birthday party. Her recipe calls for ¾ cups of brown sugar. She only has ⅓ cup left in the bag. How much brown sugar will she need to borrow from her neighbor to make the cookies?