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This lesson teaches variables and solving for unknown variables




7, 8  


Title – Variables
By – Andy Field
Primary Subject – Math
Secondary Subjects –
Grade Level – 7-8

Objectives: TLW:
1. Assign values to a variable.
2. Collect information about variables and be able to use the information to solve for an unknown variable.

Materials Needed:
For each group of 3 students: 8 small containers and 80 small countable objects code sheet prepared by teacher

SET: Explain to students that today we will play a game in which they try to solve other teams’ “Secret numbers.”

REVIEW: Go over solving equations. Ensure everyone remembers how to solve equations. Explain that today they will learn how to write equations.

1. Divide the class into groups of 3 or 4. Instruct each group to select a recorder to keep an account of the events beginning in step 6. Distribute 8 containers and 80 counters to each group.
2. Each group is assigned a different letter of the alphabet and each of the group’s 8 containers is labeled with the lowercase form of that letter. If the same lesson is taught repeatedly, the same containers can be used over and over.
3. Each group chooses a “secret number” between one and ten and informs teacher of their choice. The teacher keeps a record of all “secret numbers” on his code sheet.
4. Have each group place the “secret number of counters in each of their eight containers.
5. Each group will now have 8 containers, each of which contain the same number of counters and the same letter of the alphabet. Discuss ways to express the total number of counters in all 8 containers. For example: m+m+m+m+m+m+m+m or x+x+x+x+x+x+x+x. Build on that idea: 8m or 8x.
6. Have each group exchange some containers with one other group. For example, 3 m’s are exchanged for 3 x’s. Each group records its holdings in the following manner: m+m+m+m+m+x+x+x or 5m + 3x and x+x+x+x+x+m+m+m or 5x +3m.
7. Each group confers with the teacher who checks the code sheet to tell them the total number of counters their groups is holding. For example, the first group has 5m + 3x counters. The teacher tells them they have 22 counters.
8. Discuss if necessary how to write an equation to express the total number of counters. For example, 5m + 3x = 22.
9. Each group solves the equation they have developed to solve for the unknown variable.
10. Students continue to trade until they have discovered each group’s “secret number” or until time has run out.
11. Encourage students to keep solutions within their group so each group can make their own discoveries on their own.

Have students return to their desks. Explain that they now should be familiar with how to write algebraic expressions to represent real objects.

ASSESSMENT: Students will be assessed through informal observation and formal written evaluation on a written test.

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