Jeff Li MTP KIPP Infinity Charter School, NEW YORK, NY
8th Grade Math : Unit #5 - SYSTEMS OF LINEAR EQUATIONS : Lesson #2

# Solve systems of linear equations by graphing - with some real-life applications

Objective: SWBAT solve real-life systems of linear equations by graphing.
Standards: 8.EE.C.8 8.EE.C.8a 8.EE.C.8b 8.EE.C.8c MP1 MP2 MP4 MP6
Subject(s): Math
60 minutes
1 Warm-up - 10 minutes

Each day, students complete a warm-up that usually consists of spiraling the previous day's material, in addition to older material.  Today's Warm-up problems (WU61) also extend the goals of yesterday's lesson.

For a video narrative about how I structure each lesson, and how the warm-up fits in, click here.

A quick note - today's BRONZE problems are from Coach New York Grade 8.

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2 Play of the Day - 40 minutes
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Leading with the application of real-life systems
Real World Applications

Very early on in this unit, before we get deep into the algebra, I like to introduce the real-life application of systems.  In this case, I push the students to make an estimate of the break-even point; this pushes the understanding that the point of intersection of the graph is the place at which the two functions will have the same value.  It also pushes their number sense.  I also push the kids to make their own scales on the graphs, which further pushes this, and also to interpret the meaning of the solution.

See the attached two student samples on how students approached this task.

4 Homework - 15 minutes

HW61 Solve real-life systems of linear functions by graphing includes four problems related to this lesson.  I also give the kids the answers to the problems at the end of the assignment.

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