Notes Answers-Ratios and Proportions Lesson 17: The Unit Rate as the Scale Factor
Name _________________________Date _______________Period _____
Example 1: Rubin’s Icon
Rubin created a simple game on his computer and shared it with his friends to play. They were
instantly hooked and the popularity of his game spread so quickly that Rubin wanted to create a
distinctive icon, so players could easily identify his game. He drew a simple sketch. From the
sketch, de created stickers to promote his game. But Rubin wasn’t quite sure if the stickers
were proportional to his original sketch.
Original
Sticker
2 inches
1 inch
2 inches
1 inch
1.5 inches
0.75 inches
1 ¾ inches
7/8 inch
Steps to check for proportionality for
scale drawing and original object/picture:
1.) Measure lengths of scale drawing.
Record on table.
2.) Measure corresponding lengths on
actual picture/drawing. Record on
table.
3.) Check for constant of
proportionality.
Key Idea:
 The scale factor can be calculated from the ratio of any length in the scale drawing to
its corresponding length in the actual picture. The scale factor corresponds to the unit
rate and the constant of proportionality.
Scaling by factors greater than 1, enlarge the segment, and scaling by factors less than 1,
reduce the segment.
Notes Answers-Ratios and Proportions Lesson 17: The Unit Rate as the Scale Factor
Example 2: Flag Drawing
Create your own reduction of this flag, using a scale factor of 3.
Length
Width
Width
Width
Original Drawing
6
2
1
1
Reduction
1 ½ = 1.5
½ = 0.5
¼ = 0.25
¼ = 0.25
Notes Answers-Ratios and Proportions Lesson 17: The Unit Rate as the Scale Factor
Closing: Answer Verbally

Where is the constant of proportionality represented in scale drawings?
o Scale factor

What step(s) are used to calculate scale factors?
o Measure the actual picture lenfths and the scale drawing lengths. Write the
values as a ratio of the scale drawing length to actual picture length.

What operation(s) is (are) used to create scale drawings?
o After the lengths of the actual picture are measured and recorded, multiply each
length by the scale factor to find corresponding scale drawing lengths. Measure
and draw.