Name: ___________________________________________________________________
Date: ___________
Day2LAB: Scaled Drawings with Ratio Method
Geometry CC (M2 L2)
Opening Exercises:
1. What 2 things do we need in order to dilate a figure?
2. Using the picture below, find:
a. the center of dilation
b. the scale factor (HINT: How much did the figure change?)
3. In a well-scaled drawing, corresponding sides are in ________________________ and corresponding angles
are ____________________________.
4. If an image is larger than it’s pre-image, the dilation is described as an ________________________.
5. If an image is smaller than it’s pre-image, the dilation is described as a ________________________.
6. If we dilate a figure using our compass and it is a reduction, what do we create in order to find the
midpoints? ______________________ ________________________.
7. When two figures have sides that are in proportion and angles that are equal in measure, we call them
_________________________.
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Using the Ratio Method to Make a Scale Drawing
(CENTER OF DILATION OUTSIDE PICTURE)
What happens to the image when the scale factor is greater than 1?
Example 1 (You will need a compass and a straightedge)
Construct the image of the figure below using the Ratio Method (Use center of dilation outside picture) about center O
and scale factor r=2. ( 2 arcs each)
Connect from O to A and
extend.
Measure O to A
Arc
Do not change compass.
Point on A
Arc
Connect from O to B and
extend.
Measure O to B.
Arc
Do not chance compass.
Point on B
Arc
Repeat using C
Repeat using D
Are these figures similar? If so, how do you know?
Practice:
Use the Ratio Method to create a scale drawing according to the rule: 𝐷𝑂,3
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Partner Practice
Use the ratio method to create two scale drawings: Label the scale drawing with respect to center 𝑂 as △
𝐴′𝐵′𝐶′ and the scale drawing with respect to center 𝑃 as △ 𝐴′′𝐵′′𝐶′′.
Partner 1:
DO ,2
Partner 2:
DP ,2
What do you notice about the two scale drawings?
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What happens to an image when the scale factor is less than 1 (and greater than 0---a
fraction)?
***to dilate a scale factor between 0 and 1 we must find the _____________ of each letter
by constructing __________________ _____________________.
Example 2 (You will need a compass and a straightedge)
Use the Ratio Method to create a scale drawing according to the rule: 𝐷𝑂,1
2
Connect O to A.
Measure from O to A.
Circle
Do not change compass!!
Point on A.
Circle
Put a dot where the midpoint would be on
OA
Connect O to B
Measure from O to B.
Circle
Do not change compass!!
Point on B.
Circle
Put a dot where the midpoint would be on
OB
Connect O to C
Measure from O to C.
Circle
Do not change compass!!
Point on C.
Circle
Put a dot where the midpoint would be on
OC.
CONNECT POINTS!!!
CHALLENGE!!! (YOU CAN DO IT!)
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Create a scale drawing of quadrilateral 𝐴𝐵𝐶𝐷 about center 𝑂 with scale factor 𝑟 = 4.
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Name: _________________________________________________
Day 2LAB: Making Scale Drawings using the Ratio Method HOMEWORK
Date: _____________
Geometry CC (M2 L2)
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