standard_description: Verify experimentally the properties of dilations given by a center and a scale factor:
- A dilation takes a line not passing through the center of the dilation to a parallel line, and leaves a line passing through the center unchanged.
- The dilation of a line segment is longer or shorter in the ratio given by the scale factor.
problem_activity: Warm-up
The purpose of this warm-up is to reactivate students’ understanding of tape diagrams to make it more likely that tape diagrams are accessible as a tool for them to choose in this lesson. The diagram was deliberately constructed to encourage some students to write an equation like
\(24=3(a+2)\)
and others like
\(24=3a+6\)
. Monitor for one student who writes each type of equation.
Launch
Arrange students in groups of 2. Give 5 minutes of quiet think time and time to share their work with a partner followed by a whole-class discussion.
Student Facing
[IMG]
Write a story that could be represented by this tape diagram.
Write an equation that could be represented by this tape diagram.
Student Response
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Activity Synthesis
After students have had a chance to share their work with their partner, select a few students to share their stories. Then, select one student to share each type of equation and explain its structure:
\(3(a+2)=24\)
and
\(3a+6=24\)
.


aligns: no