Lesson 3
Making Scaled Copies
Unit i
Scale Drawings
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3.1 Warm Up: more or less?
For each problem, select the answer from the two choices.
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Learning Targets
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3.2 drawing scale factors
1. Draw a scaled copy of Figure A or B using a scale factor of 3.
2. Draw a scaled copy of Figure C or D using a scale factor of ½.
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3.3 Which Operations? (part 1)
Diego and Jada want to scale this polygon so the side that corresponds to 15 units in the original is 5 units in the scaled copy.
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3.3 Which Operations? (part 1)
Diego and Jada each use a different operation to find the new side lengths. Here are their finished drawings.
1. What operation do you think Diego used to calculate the lengths for his drawing?
2. What operation do you think Jada used to calculate the lengths for her drawing?
3. Did each method produce a scaled copy of the polygon? Explain your reasoning.
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3.4 Which Operations? (part 2)
Andre wants to make a scaled copy of Jada's drawing so the side that corresponds to 4 units in Jada’s polygon is 8 units in his scaled copy.
1. Andre says “I wonder if I should add 4 units to the lengths of all of the segments?” What would you say in response to Andre? Explain or show your reasoning.
2. Create the scaled copy that Andre wants. If you get stuck, consider using the edge of an index card or paper to measure the lengths needed to draw the copy.
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The side lengths of Triangle B are all 5 more than the side lengths of Triangle A. Can Triangle B be a scaled copy of Triangle A? Explain your reasoning.
3.4 are you ready for more?
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Lesson Summary
Scaling is a multiplicative (using multiplication) process. To draw a scaled copy of a figure, we need to multiply all of the lengths by the scale factor. We saw in the lesson that adding or subtracting the same value to all lengths will not create scaled copies.
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3.5 Cool Down: More Scaled copies
Create a scaled copy of ABCD using a scale factor of 4.
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3.5 Cool Down: More Scaled copies
given: triangle z is a scaled copy of triangle m.
Select all the sets of values that could be the side lengths of triangle Z.
a. 8, 11, and 14
b. 10, 17.5, and 25
c. 6, 9, and 11
d. 6, 10.5, and 15
e. 8, 14, and 20
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Reflections
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Practice Problems
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Lesson Video
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