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7.03 Add and subtract fractions with models

Lesson

Are you ready?

Let's review how to identify a fraction using a model. 

What fraction of the square is shaded blue?

You do not need to simplify the answer.

 

Learn

This video shows how to add fractions using an area model. 

Apply

question 1

In the image below, $\frac{1}{2}$12 has been shaded red and $\frac{3}{8}$38 has been shaded blue.

  1. Write the addition that describes the image.

  2. What is the total shaded?

Learn

This video shows how to subtract fractions using an area model. 

Apply

question 2

The image below shows $\frac{2}{3}$23 of the rectangle shaded.

  1. What is the equivalent fraction in sixths? $\frac{2}{3}=\frac{\editable{}}{6}$23=6

  2. We now want to take away $\frac{3}{6}$36.

    What is the answer to $\frac{2}{3}-\frac{3}{6}$2336?

Learn

We can also use number lines to add and subtract.  

Apply

question 3

We want to calculate the sum $\frac{1}{2}+\frac{3}{8}$12+38.

  1. Complete the statement to make an equivalent fraction for $\frac{1}{2}$12.

    $\frac{1}{2}=\frac{\editable{}}{8}$12=8

  2. Plot $\frac{4}{8}$48 on the number line.

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  3. Choose the image below that represents the addition $\frac{1}{2}+\frac{3}{8}$12+38.

    A

    B

    C

    D

 

Remember!

Think about how the denominators are related.

We can use area models to change fractions to their equivalent fraction so the denominators are the same.

 

Outcomes

5.NF.A.1

Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12 or 3/5 + 7/10 = 6/10 + 7/10 = 13/10.

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