Beacon Lesson Plan Library

Adding and Subtracting Fractions

Yunling Zhang
Palm Beach County Schools

Description

Students learn addition and subtraction of common fractions by incorporating the use of hands-on manipulatives and diagrams.

Standards

Florida Sunshine State Standards
MA.A.3.2.1.4.4
The student explains and demonstrates the addition and subtraction of common fractions using concrete materials, drawings, story problems, and algorithms.

Florida Process Standards
Numeric Problem Solvers
03 Florida students use numeric operations and concepts to describe, analyze, communicate, synthesize numeric data, and to identify and solve problems.

Materials

-Pattern blocks: 5 triangles for each student
-Papers and pencils
-Checklist (see attached file)
-Practice worksheet (see attached file)

Preparations

1. Obtain enough pattern blocks for each student.
2. Make copies of worksheet for each student.

Procedures

Prior to the lesson, students should have learned the concept of fractions and know how to write fractions through using pattern blocks.

1. Give a scenario: Tom ate one third of a cake, Bryan ate one third of the cake. What portion of the cake did they eat ? Ask students to investigate the problem by drawing two circles. Divide each circle into three equal parts. Shade one part of each circle and write the sum of shaded fractions. Ask students to write equation for this problem.You may have to model this.

2. Hand out the pattern blocks. Ask students to make a regular pentagon with 5 congruent triangles. Then ask students using the blocks to find the following fraction problems:
1/5 + 2/5 =
3/5 + 1/5 =
4/5 + 1/5 =
2/5 + 3/5 =
Manipulate pattern blocks to find the sum of the fractions. Write the equations and the answer students give to each equation on the board

3. Review the the answers. Ask students, "What should we conclude from these results? What are the steps in adding fractions?" Let students draw correct conclusion. Summarize on the board:
If adding common fractions, add the numerator and keep the denominator the same.

4. Ask students to use pattern blocks to find the answer to the following questions:
2/3 - 1/3 =
4/5 - 1/5 =

Write equations and answers on the board and then go over the answers. Ask students to say the steps they must take to subtract common fractions by subtracting one numerator from the other but keeping the denominator the same.

5. Give the work sheet to students to practice (see attached file for the sheet). Walk around to check on and assist students.

6. Go over the answers. Students redo the work they missed or was incorrect.

7. Group activity: separate the class into three or four equal groups. Each group is assigned a project. The group needs to have a leader, a writer, a reporter, and problem solvers. The reporter will demonstrate the group work at the end.

Project:

Find the number of students who have each of these eye colors in your group: blue, brown, other.
Write a fraction with the number of students for each eye color and total of the number of students in your group. Add the fractions together. Explain the steps and answer.

8. Each group demonstrates the finding and how they get their answers. Explain the process.

Assessments

Students will be assessed in variety of ways:

1. Performance-based assessment requiring students to demonstrate and explain the addition and subtraction of common fraction with pattern blocks, equations and word problems should be assessed formatively.

2. Students are assessed through teacher observation while watching students work with pattern blocks.
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