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TOC #4  Scale Factor

TOC #4  Scale Factor. Unit 5 – Staying in Shape. What is scale factor?. Scale factor: - The ratio used to reduce or enlarge similar figures. - The number we multiply an existing dimension or coordinate to find the new dimension or coordinate. What is a dilation?. Dilation:

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TOC #4  Scale Factor

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  1. TOC #4  Scale Factor Unit 5 – Staying in Shape

  2. What is scale factor? • Scale factor: - The ratio used to reduce or enlarge similar figures. - The number we multiply an existing dimension or coordinate to find the new dimension or coordinate.

  3. What is a dilation? • Dilation: - The type of transformation where a figure’s size is increased or decreased.

  4. Scale factor < 100%reduces a figure • Less than 100% means multiplying by a number less than 1. • The new figure will be reduced in size. 

  5. Scale factor = 100%keeps a figure the same • Equal to 100% means multiplying by 1. • The figure will be the same or congruent. 

  6. Scale factor > 100%enlarges a figure • Greater than 100% means multiplying by greater than 1. • The figure will be enlarged or greater in size. 

  7. Using scale factor…example #1 • A rectangle has a length of 4cm and a width of 3 cm. Find the new dimensions with a scale factor = 4.

  8. Using scale factor…example #2 • A triangle has a base of 4.5 cm. What is the length of its base with a scale factor of 5cm?

  9. Using scale factor…example #3 • A rectangle has a length of 12m and a width of 8m. What are the dimensions of a similar rectangle with a scale factor of 0.5?

  10. Using scale factor…example #4 • The coordinates of point A are at (4, 5). What would the new coordinates be after a scale factor of 3 is applied?

  11. Scale factor and area • Given the two rectangles below, find the area of the first rectangle and then the area of the second. 2m 6m 3m x

  12. Scale factor and area…

  13. Scale factor conclusions • The scale factor for AREA: - The scale factor for the outside dimensions squared. • Unless it is specified, scale factor will refer to the ratio of the side lengths NOT the scale factor of the area.

  14. Working backwards… • If a rectangle has an area of 6 square units, and its copy has an area of 24 square units, find the scale factor. 1st find the scale factor of the area: 6 x ? = 24 ? = 4 2nd “un-square” it to find the scale factor for the figures dimensions. 4 = ? x ? Scale factor = 2

  15. Homework… • Complete the handout “Using Scale Factor”

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