How to Add Fractions with Unlike Denominators

adding fractions with unlike denominators
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Welcome, upper elementary teachers! Teaching students how to add fractions with unlike denominators can be a daunting task. But we’ve got you covered. In this lesson plan, we will break down the steps and provide an easy-to-follow outline that you can use while teaching your class. Plus, you can use my downloadable free question sheet at the end of this blog post to provide your students with practice.

Introduce Adding Fractions with Unlike Denominators

Let’s begin by introducing our topic: fractions. Explain to your students that a fraction is part of a whole number represented by two numbers written above a line (the numerator) and below the line (the denominator). For example, 2/3 is equal to two-thirds of a whole number.

Now let’s move on to adding fractions with unlike denominators.

Step One: Find the Least Common Multiple

The first step is to list the two fractions with their denominators. Then, we need to find the least common multiple (LCM). To do this, you can use a variety of methods. I suggest that you ask students to list out the multiples of each number until they find a number that both denominators will divide into. You can also use a chart/diagram to illustrate how different numbers relate to each other and discover common factors.

Let’s say we have the fractions 2/3 and 4/5. To find the LCM, we need to list out their multiples:

2/3: 3, 6, 9, 12, 15

4/5: 5, 10, 15

The LCM of 2/3 and 4/5 is 15.

Step Two: Convert the Fractions to Equivalent Fractions with the Same Denominator

Once we have the LCM, we can convert both fractions so they have the same denominator. To do this, we must multiply both numerators by a certain number that will make their denominators equal to the LCM.

For 2/3: Multiply the numerator (2) by 5 and multiply its denominator (3) by 5 so it becomes 10/15.

For 4/5: Multiply the numerator (4) by 3 and multiply its denominator (5) by 3 so it becomes 12/15.

Step Three: Add the Numerators

Now that both fractions have the same denominator, we can simply add their numerators together to get our answer.

In this example, 10/15 + 12/15 = 22/15

So, our final answer is 22/15.

Step Four: Convert Improper Fractions to Mixed Numbers

If the answer results in an improper fraction (a fraction with a numerator larger than its denominator), you can convert it to a mixed number. To do this, divide the numerator by the denominator and write down the whole number as your answer. Then, take the remainder of that division and put it over the original denominator.

For example: 22/15 = 1 7/15

This means that our final answer is 1 7/15.

Congratulations! You’ve successfully added two fractions with unlike denominators! To help your students practice this skill further, feel free to provide some practice handouts or worksheets at the end of this lesson plan.

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