Page 99 - Math Course 2 (Book 2)

Transformations: Dilations

Determine the scale factor used for the dilation The photograph’s dimensions are given in centime-
with center C. Determine whether the dilation is ters, and the frame’s dimensions are in millimeters.
an enlargement, reduction, or congruence You need to convert from millimeters to centimeters
transformation. in the problem.

Step 1 Convert from millimeters to centimeters.

400
400 millimeters = or 40 centimeters
10
Step 2 Find the scale factor.

image length
scale factor =
preimage length

40 frame length
=
20 photo length

image length = 2 Simplify.
scale factor =
preimage length

5 image length Sharetta used a scale factor
= Answer of 2 to build the frame.
5 preimage length

= 1 Simplify.
Your Turn!

Since the image falls on the opposite side of the
center, C, than the preimage, the scale factor is Identify Scale Factor
negative. So the scale factor is –1. The absolute For the green preimage, determine the scale factor
value of the scale factor equals 1, so the dilation used for each dilation with center C. Determine
is a congruence transformation.
whether the dilation is an enlargement, reduction,
or congruence transformation.
–1 ; congruence
Answer
transformation A. 2; enlargement
1
B. ; reduction
2
1
Scale Drawing C. ; reduction
3
Examples D. 1; congruence
transformation

Sharetta built a frame
for a photograph that
is 20 centimeters by 25
centimeters. The frame
measures 400 millimeters
by 500 millimeters. Which
scale factor did she use?
Answer

91