Intro to Dilations

dilation: a transformation that enlarges or reduces a figure

​​scale factor (K): the ratio of corresponding sides in similar figures; the multiplier used to create a new image shape or figure after a transformation

​​pre-image: a shape or figure before a transformation; the original figure

​​image: a shape or figure after a transformation; the new figure

​congruence: when two figures are the same size and same shape

​dilation similarity: when two figures are the same shape and have proportional sides and congruent angles (not the same size)

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​On the previous slide we learned that to dilate a figure you multiply by the scale factor.

​ Using an Inspire Calculator

• ​Multiply 15 (2/5)

• ​Multiply 35 (2/5)

​​The new dimensions are 6in by 14 in

​This makes sense since the Scale factor is less than 1 the new image will be smaller.

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​Now complete 6&7

​Scale Factor = new divided by the old.

​​​First identify the corresponding/ similar sides in the figures.

• ​ EX: Side GH which is 8cm corresponds to side G'H' which is 10 cm.

​Take any of the matching sides and divide the new measure by the old measure.

• ​Notice how the new image is larger than the pre-image. This is because the Scale factor is greater than 1.

Now ​Complete Number 9

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