Light it Up – Day 2: Modeling with Rational Functions

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SWBAT write rational functions that model problem situations and use these equations to solve problems.

Big Idea

Students will investigate the Light it Up game and find a rational equation that will help Bart and Lisa to win this game every time!

Warm-up: Review Homework

5 minutes

As we begin Day 2 of this lesson, it is essential that students are able to write the equation for a rational function by interpreting a graph where a clear shift is evident. Some students will also be able to write an equation for a graph involving a stretch factor. In order to assess students' status with respect to these issues, I will begin today's class by reviewing last night’s homework (Question 8 on the Light It Up worksheet).

To facilitate homework review, I am going to divide the whiteboard into four sections labeled A-D and ask students to write the equation they found for each graph in the appropriate section. I don't want duplicates, but I will ask students to keep writing equations as long as their equation is not already posted. I want this to happen as students are entering the classroom, which will provide some measure of anonymity.

Once all of the students arrive, I will lead a class discussion in which we identify the correct equations as a class. I am hoping that by looking at some incorrect answers, as well as correct answers, the conversation will address both misconceptions and correct mathematical work.

Investigation: Light it Up

30 minutes

After the Warm-up students will spend the rest of the period collecting data for the Light it Up game and finding the equation that models this situation (pg. 11-12 of original Light It Up activity sheet). 


Teaching Notes:

  • Today's lesson was adapted from the lesson Light It Up on the National Council of Teachers of Mathematics Illuminations website. The lesson can be found here (accessed March 6 2014)
  • Check out Light it up, video narrative for an overview of my plans for the lesson over the next two days. In the video I also discuss the mathematical practices I expect students to engage in during the lesson.



5 minutes

As a closure to today’s lesson, I am going to have teams text in their answers to part f, the equation that models the light it up game. This closure will have two purposes. First, it will hold students accountable to get to the equation before the end of the class period. And secondly, students’ responses will help lead a class discussion about the correct equation. I plan to keep teams’ responses anonymous so we can discuss what is correct and what is incorrect about each answer without putting kids on the spot. I think it is important for students to verify they have the correct answers before they leave class today. If mistakes were make, it will be a good learning opportunity for students.


At the end of the lesson I will assign Homework 6 - Rational Functions from this unit.