Reflection: Lesson Planning Ratios and Scale Factors - Section 2: Intro to New Material


By the time we get to this lesson, there are students who have already thought about using a multiplicative relationship, rather than repeated addition.  They may not know the term for scale factor, but they're able to see that multiplication would be a more efficient strategy.

It's an intentional choice to not introduce scale factor until late in this unit.  I believe that it's important for students to understand the constant change between equivalent ratios.  I want students to understand that not all fractions are ratios (which is a misconception that I think can happen more easily if the jump is made too quickly to scale factor).  

If, in earlier lessons, students ask about using multiplication, I absolutely encourage them to try it out.  I want them to decide if its a strategy that works all of the time.

This lesson sets the stage for more rigorous problems in the next unit, Unit Rate Applications and Percents.  I want students to get comfortable with the concept of scale factor and practice applying it.  In the next unit, students will need to use rational numbers more often, including as the scale factor.  The idea here is to set the stage for where we're going next.

  Setting the Stage for Future Lessons
  Lesson Planning: Setting the Stage for Future Lessons
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Ratios and Scale Factors

Unit 5: Rates and Ratios
Lesson 9 of 13

Objective: SWBAT express equivalent ratios by using scale factors to create double number lines and tables

Big Idea: We can create equivalent ratios using a scale factor instead of adding repeatedly.

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9 teachers like this lesson
Math, Number Sense and Operations, scale, scale factor, ratio of whole numbers, ratio tables, ratios, double number line
  60 minutes
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