Education Technology

Expressions and Equations / Visualizing Systems of Linear Equations

Grade Level 8
Activity 15 of 18
In this lesson students will reason about solutions to systems of equations while modeling the systems on mobiles.

Planning and Resources

Students should be able to write algebraic equations using variables that represent the relationship among the values of shapes on a mobile, associate moves that preserve balance in the mobile with moves that preserve algebraic solutions, and find solutions to systems of linear equations in more than one variable.

system of linear equations in two variables

Standard: Search Standards Alignment


Lesson Snapshot


Students understand how mapping balanced mobiles to a system of equations provides a foundation for reasoning about strategies for solving systems of equations.

What to look for

Some students may reason about the numerical value for each expression in an equation and how they must be the same, while others may reason by identifying numbers that make the mobile unbalanced and in which direction.

Sample Assessment

"A store sells white scarves and red scarves. A white scarf costs $3 and a red scarf costs $5. On Monday, the store sold 12 scarves for a total of $50. What is the total number of red scarves that the store sold on Monday?

a. 4
b. 5
c. 6
d. 7

Answer: d

The Big Idea

A sense of the relationship among variables under different constraints can be developed in the context of mobiles.

What are the students doing?

Students reason about the values of weights on mobiles and use balance to model solution preserving moves algebraically.

What is the teacher doing?

Encourage students to use the way the mobile behaves to reason about the values of weights on the mobiles and relate that to the values of variables in a system of equations.