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# Define, Set, Go!

Lesson 8 of 14

## Objective: SWBAT interpret a word problem, define variables and set up a system of equations. SWBAT solve the system using the linear combination method.

#### Warm up

*10 min*

In this warm up, I focus on the importance of defining the variables in mathematical modeling (**Math Practice 4**). The context for this warm up is Warm Up: Ordering Softballs. Students will define a system that can be used to identify how many of each size of softballs were in the original order.

I plan for this task to take about five minutes for the students to complete. I will use another five minutes to review the warm up with the students to introduce the goals of the lesson.

After defining the variables, I again review with students how to write the equations from the constraints given in the problem. I model writing the equations, and solving using elimination in the video below.

#### Resources

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#### Guided Practice

*30 min*

In these guided problems I first work with students to define the variables. Then, we work together to set up the equations. I walk around the room to monitor students. I provide one-on-one help to students who need it. Then, I ask students to begin working on solving the equations using elimination. The worksheet includes a graphic organizer for each problem to organize each step of the process.

Students need to be able:

- Define the variables
- Write equations modeling the problem
- Use the properties of algebra to solve the system of equations
- Identify and interpret the solution to the problem

In order to emphasize Math Practice 6, I require that students label their answer to the final questions with correct units.

#### Resources

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#### Self-Reflection

*10 min*

To end the lesson, I use a Self Reflection as a formative assessment. I want to provide each student with an opportunity to assess his/her ability to solve linear combination problems. I decided to use self-reflection instead of peer grading because there are so many different parts and details to determine the mistakes or misconceptions. I think it is helpful for students to see their own mistakes working through the worksheet, to provide immediate feedback.

At the end of the unit, on a summative assessment, students are able to solve a system of equations using any method, as long as the solution is supported with mathematical and verbal reasoning. For this assignment, I provided specific procedures for to setting up the problem, defining the variables, writing the equations, and describing the solution.

#### Resources

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- UNIT 1: Introduction to Functions
- UNIT 2: Expressions, Equations, and Inequalities
- UNIT 3: Linear Functions
- UNIT 4: Systems of Equations
- UNIT 5: Radical Expressions, Equations, and Rational Exponents
- UNIT 6: Exponential Functions
- UNIT 7: Polynomial Operations and Applications
- UNIT 8: Quadratic Functions
- UNIT 9: Statistics

- LESSON 1: Introduction to a System of Linear Equations
- LESSON 2: The Best of 2 Cell Phone Plans
- LESSON 3: Who is 1st in the Father Daughter Race?
- LESSON 4: Can You Save The Diver in 7 Minutes?
- LESSON 5: Make a Substitution
- LESSON 6: Alternate Method to Solve a System of Equations by Substitution
- LESSON 7: Quarters, Dimes and Linear Combinations
- LESSON 8: Define, Set, Go!
- LESSON 9: Khan Your Way Into Solving a System of Equations Using Elimination
- LESSON 10: Elimination with 2 Column Notes
- LESSON 11: Assessment of a System of Linear Equations
- LESSON 12: Use The TI-Nspire CX To Solve a System of Equations
- LESSON 13: Solving a System of Inequalities
- LESSON 14: Solve the System of Inequalities to Find The Treasure!