Lesson 5 — Activity 2: Working with Fractions with UnLike Denominators
Lesson 5 — Activity 2: Working with Fractions with Unlike Denominators
In the last activity, you practised adding and subtracting fractions and mixed numbers with the same denominator.
Now you will look at fractions
where the denominators are not the same. It is necessary to make them
the same before you can add or subtract a fraction.
Let's look at an example:
You have allowed yourself half of your allowance to spend on books.
You can get a common denominator by finding the equivalent fractions with the lowest common denominator (LCD).
Here is a problem for you to solve.
A punch recipe calls for 3/4 cups of pop and 2/3 cups of juice.
How much punch will there be in total?
1. Find the lowest common multiple of the denominators. This will be the lowest common denominator (LCD).
Multiply each fraction by the number of times the denominator goes into
the LCD. Remember to multiply both the top and the bottom.
3. Make an equation with your new fractions and solve. You will have an improper fraction as your answer!
Your answer for the above problem was an improper fraction.
Before you are done with the problem, you must reduce this improper fraction by dividing the denominator into the numerator.
There will be 1 5/12 cups of punch in total.
Let's now try the punch problem using mixed numbers.
The punch recipe calls for 2 1/4 cups of pop and 2/3 cup of cranberry juice. How much punch will there be in total?
Then do the following: