Develop a more precise definition of similar. The lesson begins with an informal definition of similar figures and develops the need to be more precise. The class learns about dilations and uses that knowledge to arrive at a mathematical definition of similar.  

Concepts

dilation, dilations, scale factors, scale, similarity, similar figures

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Additional Tags

math

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Instructional Ideas

• Provide dilations of line segments and have the class draw them
• Make it clear that class members must use the ratio of the lengths to find the scale factor

Classroom Considerations

• The class should be familiar with the concept of congruence
• The resource is the first in a series of 16

Pros

• The answer keys use the notation from the lesson to create the equations
• The exit tickets assesses both the conceptual understanding the computation associated with dilations

Cons

• The resource does not contain an embedded movie as stated

Common Core

8.G.A.3