Working Backwards with Percents - What happens when a problem is not straightforward?

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Students will be able to work backward in a percent problem to find the original price.

Big Idea

You can apply percents - but can you work backwards to find them? This lesson gives students an opportunity to unravel percent problems.


10 minutes

OpenerAs students enter the room, they will immediately pick up and begin working on the opener – Instructional Strategy - Process for openers.  This method of working and going over the opener lends itself to allow students to construct viable arguments and critique the reasoning of others, which is mathematical practice 3

Learning Target:  After completion of the opener, I will address the day’s learning targets to the students.  For today’s lesson, the intended target is, “I can work backward in a percent problem to find the original price.” Students will jot the learning target down in their agendas (our version of a student planner, there is a place to write the learning target for every day). 

Thoughts from Me!  As students begin to work on problems, they will be looking for patterns and/or repeated reasoning (mathematical practices 7 and 8).  What types of problems require division? Students will need to be precise when determining the information they are given so that they are able to accurately find the missing value (mathematical practice 6).  


45 minutes

Working Backwards Notes:  Working Backwards Video

White Board Practice:  During this portion of the lesson I am going to ask that students flip over their notes sheet in order to access their "built in scrap paper." While one group member writes on the board, the others should write on their scrap paper :) The board should rotate around the table so that all students at the table get to write on the board.  The questions in this activity are a mix of applying a percent to find a mark up or down, and then undoing a problem to find an original value.  Separately, students will not have any trouble.  However, as the problems begin to become mixed - students will have to identify what information they have so that they can choose the correct steps for solving it.

Summary + Homework

5 minutes

Instructional Strategy - Table DiscussionTo summarize this lesson, I am going to ask that students have a table discussion on the operations involved in working backwards.  As I mentioned earlier in the lesson, we are using inverse operations to “undo” what has already been done in a problem – this is an application of one step equations, which have been taught previously within the common core.  I will have tables share out their thoughts before I summarize the feedback from all tables.  

Homework:  As tables share, I will pass out the homework, as to better be able to hear what they talk about :)