August 3, 2017
by Byron Delcomb

Lesson plan

Scale, Shapes, and Sets

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Students will be able to calculate scale dimensions and predict next shapes to scale in a set.

(5 minutes)
  • Draw two lines in front of your students, one twice as long as the other labeled 4 cm and 2 cm respectively.
  • Have your students think, pair, and share the answer to this question, "What kind of relationship do these two lines have to one another?”
  • Allow student responses and draw a connection to the fact that these two lines are in scale with one another: the longer line is two times the scale of the shorter one.
  • Write the following, “The shorter line is [blank] times the scale of the longer one.” Have your students think, pair, and share the missing amount.
  • Direct the whole class to share-out of answers and reasonings.
  • Confirm the answer to be 1/2.
  • Explain that scale is the amount a measurement is multiplied by to create proportional model. Shapes are proportional to one another if their internal angles are the same. This lesson will focus on proportional shapes.
(10 minutes)
  • Hand out and preview the Predicting Shapes to Scale worksheet.
(10 minutes)
  • Lead your class through the first exercise of the Predicting Shapes to Scale worksheet and answer any clarifying questions.
(15 minutes)
  • Release your students to complete the remaining exercises of the Predicting Shapes to Scale worksheet.


  • Use sentence frames to scaffold student thinking around the idea of scale, like: “The dimension of the larger item is [blank] times to scale of the smaller item in the set” and “The dimension of the smaller item is [blank] times to scale of the larger item in the set.”


  • Have students calculate dimensions for two or more items, larger and smaller in each set.
  • A computer with internet access and projector makes for a great setup to display proportional models to scale.
  • Additional information on scale or "scale factor" is expressed clearly in the video, How to Calculate Scale Factor, listed in the related media section.
(5 minutes)
  • Show your students a shape with a measurement of at least one feature and have them describe up to two additional scaled items for a set.
(10 minutes)
  • Have your students:
    • Share out their answers.
    • Allow others to challenge answers to dispute claims.
    • Phone a friend for support to take over explanations when they need assistance.

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