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Objective

Common Core State Standards

■ 4.NF.3a

■ 4.NF.3d

4Number and Operations—Fractions

Add and Subtract FractionsStudents will need to add and subtract fractions when they begin working with measurements. Sometimes the fractions will have like denominators and other times they will have unlike denominators. In this lesson, students will add and subtract with like denominators.

Talk About ItDiscuss the Try It! activity.

■ Ask: How do we add or subtract fractions when they have like denominators?

■ Ask: Can we use subtraction to check our work when adding fractions? How?

■ Ask: Can we use addition to check our work when subtracting fractions? How?

Solve ItWith students, reread the problem. Have students draw a rectangle to represent the mural. Then have them label the sections that the third and fourth graders will paint. Have students write a number sentence for the fraction of the mural that the third and fourth graders are painting and a number sentence for the fraction the fifth graders are painting.

More IdeasFor other ways to teach about adding and subtracting fractions—

■ Give students a problem that involves adding or subtracting fractions with like denominators. Students can use Fraction Circles to help them solve the problem.

■ Have students grab eight random Color Tiles from a bag or box, then come up with a fraction to represent one of the colors of tiles, such as “ 2 __ 8 of the tiles are red.” Then have students use addition and subtraction to model the pile based on that Color Tile, for example, “8 __ 8 – 2 __ 8 = 6 __ 8 of my group is not red.” Challenge students to use addition to check their problems, for example, “ 2 __ 8 + 6 __ 8 = 8 __ 8 .”

Formative AssessmentHave students try the following problem.

Tenysha has 1 __ 6 of her muffin left. Anna has 3 __

6 of her muffin left. Between the

two of them, what fraction of a muffin do they have?

A . 4 __ 12 B . 2 __ 6 C . 4 __ 6 D . 5 __ 6

Number and Operations—Fractions

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Materials• Fraction Tower® Equivalency Cubes

(1 set per group)• paper (2 sheets per group)• pencils (1 per group)

Try It! 30 minutes | Groups of 4

Here is a problem about adding and subtracting fractions.

The third, fourth, and fifth graders at Liberty Elementary School are painting

a mural to celebrate school spirit. The third graders will paint 1 __ 6 of it, and

the fourth graders will paint 2 __ 6 of it. What fraction of the mural will the fifth

graders paint?

Introduce the problem. Then have students do the activity to solve the problem. Distribute materials to students.

1. Write 1 __ 6 + 2 __

6 on the board. Have students

model the problem with one 1 __ 6 cube and a tower of two 1 __ 6 cubes. Explain to students that when the denominator is the same, they add the numerators. Have students add the fractions.

3. Ask: What is the difference? Let students find that a 3 __ 6 tower completes the whole, so the difference is 3 __ 6 . Have students write the difference as a number sentence.

2. Elicit that 1 __ 6 + 2 __ 6 = 3 __ 6 is the fraction of the mural painted by the third and fourth graders. Ask: How could we represent the fraction painted by the fifth graders? Have students place a 3 __ 6 tower next to the whole and elicit that the difference between the whole and the 3 __ 6 tower is the fraction painted by the fifth graders.

Students might want to represent the section of the mural the fifth graders paint as 1 __ 2 . Explain that 1 __ 2 is correct, but that in this lesson they are working with like denominators, so they should work with sixths. Tell students they will work with unlike denominators in the future.

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Hands-On Standards, Common Core Edition

4

Use Fraction Towers to model each sum or difference. Write the fractions and the answer.

1. +

_____________ + _____________ = _____________

2. –

_____________ – _____________ = _____________

3. + +

__________________ + _____ + _________________ = ________

Using Fraction Towers, model each sum or difference. Then sketch the models below. Complete the equation.

7. 3 ___ 12 + 7 ___ 12 = ______

10. 8 ___ 10 – 5 ___ 10 = ______

8. 9 ___ 10 + 2 ___ 10 = ______

11. 4 __ 5 – 1 __ 5 = ________

Find each sum or difference.

9. 8 ___ 12 + 2 ___ 12 + 5 ___ 12 = ____

12. 5 __ 6 – 2 __ 6 = ___________

4. 2 __ 5 + 1 __ 5 = ________ 5. 6 __ 8 – 3 __ 8 = ________ 6. 2 ___ 10 + 7 ___ 10 = ______

Answer Key

Download student pages at hand2mind.com/hosstudent.

(Check students’ work.)

3 __ 8

2 __ 5

3 __ 5

10 ___ 12

3 ___ 10

11 ___ 10

3 __ 5 3 __ 6

15 ___ 12

3 __ 8 9 ___ 10

6 ___ 12 1 ___ 12 4 ___ 12 11 ___ 12

2 __ 8

1 __ 5

5 __ 8

1 __ 5

(Check students’ models.)

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Hands-On Standards, Common Core Edition

Challenge! Show 3 __ 4 + 3 __ 4 on a number line.

Answer Key

Download student pages at hand2mind.com/hosstudent.

Challenge: Check drawings. Students should mark off 2 intervals, 0 to 3 __ 4 and 3 __ 4 to 1 2 __ 4 , or 1 1 __ 2 .

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Hands-On Standards, Common Core Edition

4

Use Fraction Towers to model each sum or difference. Write the fractions and the answer.

1. +

_____________ + _____________ = _____________

2. –

_____________ – _____________ = _____________

3. + +

__________________ + _____ + _________________ = ________

Using Fraction Towers, model each sum or difference. Then sketch the models below. Complete the equation.

7. 3 ___ 12 + 7 ___ 12 = ______

10. 8 ___ 10 – 5 ___ 10 = ______

8. 9 ___ 10 + 2 ___ 10 = ______

11. 4 __ 5 – 1 __ 5 = ________

Find each sum or difference.

9. 8 ___ 12 + 2 ___ 12 + 5 ___ 12 = ____

12. 5 __ 6 – 2 __ 6 = ___________

4. 2 __ 5 + 1 __ 5 = ________ 5. 6 __ 8 – 3 __ 8 = ________ 6. 2 ___ 10 + 7 ___ 10 = ______

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Hands-On Standards, Common Core Editionwww.hand2mind.com

Challenge! Show 3 __ 4 + 3 __ 4 on a number line.