# Introduction to systems of equations

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## Objective

Students will be able to set up a system of equations that can model a real world situation. Students will understand how the constraints of a system of linear equations leads to one simultaneous solution.

#### Big Idea

This lesson gives students a hands on approach to learning about systems of equations with something that they can all relate to...money! By placing constraints on the value of coins and the number of coins students see that there is only one way to meet

10 minutes

## Investigation

10 minutes

During this portion of the lesson students will work with their partner using the coins to determine the appropriate combination of coins that will make the constrain equations true.  I let all students go through and answer questions 1-5 first but leave the "equations" column blank.  If students complete the task early they can attempt problems 6-8.  Once all students have completed 1-5 we go back to write our algebraic representations.  It is very important that we write a good description of our variables: e.g. n = the number of nickels and p = the number of pennies. Students can then write the constraint equations for each problem: e.g. 5n+p = 11 and n + p = 3.  This is a good time to show how substituting the values that students came up with intuitively will make both equations true.

## Closure

10 minutes

The objective of this lesson was to move students from a concrete understanding of constraint equations to being able to represent these constraint situations algebraically.  The closure of this lesson (which I have student put on index cards or half sheets of paper as a ticket out) requires students to write one algebraic expression and one algebraic equation to represent two scenarios.  The understanding of how to write these representations will be crucial for student success through the remainder of the unit.