Heather Stephan WESTERN MIDDLE, ELON, NC
7th Grade Math : Unit #7 - Geometric Figures : Lesson #3

Scale Factor

Objective: Students will be able to determine scale factor.
Standards: 7.G.A.1 MP1 MP2 MP3 MP4 MP7 MP8
Subject(s): Math
60 minutes
1 Launch - 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 determine scale factor.” 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). 

Activating Prior Knowledge:  To get this lesson started, I like to pose the following problem:  The scale of a blueprint is 1 inch = 10 feet.  The scale factor is 1 : 120.  So what is scale factor? What does it tell you? How did I get 1 and 120?  I let tables discuss this problem for a few moments and take volunteers to share out their answers to the group.

2 Explore - 45 minutes

Scale Factor Notes:  Explore Video  The notes portion of the lesson gives students an opportunity to get a grasp on what scale factor is, and why it is acceptable to drop the units when using scale factor.  Additionally, students get an opportunity to work out problems involving scale factor.  My suggestions to them is to think of their unit rate in terms of model/actual instead of using their units - since their units are the same! 

Scale Factor Practice:  For the practice portion of the lesson, I am going to give the kids a worksheet as well as the whiteboards.  I want all students to work the problems out on their worksheet as well as place their answer on the white boards for a quick check for understanding by me.  The reason for the worksheet is that I want students to have a reference to go back to when they start to study for a test - what kinds of problems did we go over in class?  While I like to use whiteboards and table challenges on a regular basis...I also think it is important that they have examples in their hands. 

This lesson brings in mathematical practice 2 and 4 - as students are applying what they know to real world scenarios - and they are taking a value given as a scale or scale factor and using it to solve problems.  Attention to detail in terms of setting up the unit rate is also very important, as putting the wrong number in the numerator could spell disaster! (mathematical practice 6)

3 Summary - 5 minutes

 Instructional Strategy - Table Discussion To summarize this lesson, I am going to ask that students have a table discussion on the question – what does a scale factor of 1:24 mean – what does it tell you?  It is important that students understand that scale factor does not involve units, it simply is a way to compare an original to a scale drawing/figure.  

Summary Reflection
Flexibility

I never made it to the summary today!  The concept of scale factor took longer for some students to grasp than I anticipated, so I slowed the lesson down and we barely squeezed in the practice work.  The next time I teach this lesson I will probably split it into two lessons - one focused on converting the units, and one using the scale factor to solve problems.