Shapes to Scale
Students will be able to predict and explain features of shapes that are scaled by factors greater than one.
- Show your class two pictures: A model of something, and a picture of the actual item.
- Ask, “Which one is the is the real item?” Allow for student responses.
- Reveal which picture was a model. Note how a model is a version of something, but wouldn’t be very realistic, if it weren’t ‘to scale,’ or have the same features in proportion to the real thing.
- Explain that establishing features in proportion to scale means to multiply all of the dimensions by the same factor.
Explicit Instruction/Teacher modeling(10 minutes)
- Explain that today’s lesson will focus on scaling regular figures (those with equal side lengths) while showing your class a paper cut-out square with 4-inch sides.
- Then, show your students another square with 8-inch sides. Have your class turn and share with a partner how both square compare to one another.
- Allow several students to share their ideas with the whole class. Tell your students that the two squares are ‘to scale.’ The smaller square side length has been scaled by 2 (or multiplied by 2) to create the larger square.
- Allow for students to turn and tell a neighbor how they might explain this idea in their own words.
Guided Practice(5 minutes)
- Hand out copies of the Scaling More Regular Shapes worksheet.
- Preview the entire sheet and review the example with your class. Answer any clarifying questions.
Independent working time(15 minutes)
- Have your students complete the exercises for the Scaling More Regular Shapes worksheet.
Enrichment: Students can make scaled diagrams of non-regular angular shapes like rectangles, triangles and trapezoids.
Support: Students can start off by practicing up-scaling regular shapes by two, moving on to three and four times.
- Show your students two shapes labeled A and B. Shape A is scaled by a factor of 5 to create B. Ask students to show fingers that show the scale factor used from shape A to create shape B.
Review and closing(10 minutes)
- Have students share out their answers, and if others disagree, allow for challenges. Allow for at least two before clarifying correct answers, if necessary.