Understanding Dilations and Scale Factors

Understanding Dilations and Scale Factors
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Learn about dilations, scale factors, and the center of dilation, with examples of enlargements, congruent figures, and reductions.

About Understanding Dilations and Scale Factors

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1. Notes Dilations

2. Definitions Dilation - a transformation in which every point P has an image P' placed on OP so that and OP' = k * OP Center of Dilation – the point from which an original figure is dilated. Scale Factor - the ratio of the image length to the corresponding original length.

3. Scale Factor • If the scaled factor is greater than 1, then it is an enlargement (k>1) . • If the scaled factor is equal to 1, then it is a congruent figure (k=1) • If the scale factor is less than 1, then it is a reduction (k<1) .

4. Corresponding distances 4 2 = = 2 Image Distance Original Distance = k Scale Factor 2 > 1 This dilation is an enlargement .

5. Corresponding distances 2 3 = Image Distance Original Distance = k Scale Factor 2/3 < 1 This dilation is an reduction .

6. Example: 1. Rectangle W ’ X ’ Y ’ Z ’ is the image of rectangle WXYZ after a dilation. a. Find the scale factor of the dilation. b. Tell whether the image is a reduction or an enlargement .

7. Example: 2.

8. Example: 3.

9. Reduction, Enlargement, or Congruent? 1. K = 4 2. K = ½ 3. K = 1 4>1 Enlargement ½ <1 Reduction Congruent

10. Matching A. K = ¼ B. K = 3 C. K = 2/7 D. K = 1 E. K = 5 F. K = 3/8 Reduction Enlargement Congruent

11. 7. scale factor 2

12. 8. scale factor ¼

13. 8. scale factor 1/3

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