Lesson Plan

Can You Get Past The Troll?

A tale of adventure where you must use linear systems to get past the troll guarding the bridge.
Rick B.
Classroom teacher
Huntington Middle School
Huntington, United States
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My Grades 8
My Subjects Math

Students will be able to...

Take a semi-real world context and use linear systems to find a solution to the scenario presented.


Common Core Standard


8.EE.8 - Analyze and solve pairs of simultaneous linear equations.

Grades 8 – 9
All Notes
Teacher Notes
Student Notes

1 Hook

Students are presented with the problem described at Khan Academy, in the presentation Trolls, tolls, and systems of equations.  They will be shown the first half of the video, stopping short of Sal's explanation of how to solve the problem to foster discussion about how to approach this problem.  The students are provided with the scenario and the information that is important to the situation.  After the discussion, the rest of the video will be completed to see if our assumptions were correct.

As students listen to the scenario unfold, they are provided with the information they need to complete the task and should immediately begin to think back to their knowledge of linear equations in two variables (linear functions).  

Many students are starting to explore the worlds of Science Fiction/Fantasy in their reading, and using this troll scenario will allow you to reach many of them by engaging them in an interest they hold.

2 Direct Instruction

After a short discussion of the introduction video for the troll scenario, the students will then be shown the next video Solving the Troll Riddle Visually. As the video is played, the students will be allowed to raise their hands, if they have a question about the demonstration, and the video will be paused to answer the questions at hand.

3 Guided Practice

Students will then be shown the video Solving Systems Graphically video from Khan Academy.   They will be shown this in preparation for the Independent Practice section of the lesson.  

4 Independent Practice

Students will be asked to complete work, on computers, iPads, and other devices at Graphing Systems of Equations at Khan Academy.  The students will have the chance to practice the skills on the site and keep track of their progress by signing in via a Gogle account login.  The teacher during this time, will move about the classroom and work with the students as needed to soldify understanding.

5 Wrap-Up

Finally, the teacher will present the students with a new scenario for students to find a solution, similar to the Troll Scenario.  The scenario will be posted on the teacher's class website.  Students will then work in groups to come up with a resolution using Desmos to great their graphs and write a short report on their findings.  Their report should detail what they did to find their solution, including the equations they created, why they created them, and the graph of the equations showing the point of intersection of the graphs (giving them their solution).