Adding and Subtracting Fractions with Unlike Denominators: Using the Area Model

1. Adding and Subtracting Fractions with Unlike Denominators:Using the Area Model MATH 8 Ms. Stewart Outcome: B5Add and subtract fractions concretely, pictorially, and symbolically B6 Add and subtract fractions mentally, when appropriate

2. How do you add fractions with unlike denominators? We will be learning about how to solve this type of question by creating area models… For example:

3. Quick (but important!) Review

4. Quick (but important!) Review This fraction represents one out of 3 equally sized parts of the whole The denominator also names the size of the part, so we know that each of these parts is a third

5. Common Denominator In order to add numbers together, we must use the same unit. For example: 4 apples + 3 bananas = ?

6. Common Denominator Can we find a common unit for apples and bananas? What about pieces of fruit? 4 pieces of fruit + 3 pieces of fruit = 7 pieces of fruit The same principle applies to fractions, in order to add fractions together, we need to have a common denominator (the same unit!)

7. Using Area Models From our models, it is clear to see that we cannot not add these fractions together yet, because the pieces represent different units.

8. Using Area Models In order to add these two fractions we need to find a common denominator. To find a common denominator we are going to combine these two models: First, we will equally divide our model of ½ into 5 equal parts Now we have fractions of the same unit and can simply add!

9. Add up the area…

10. Your turn…