1. use the similar parallelograms below. a)find their scale factor. b)find the ratio of their...
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1. Use the similar parallelograms below.a) Find their scale factor.b) Find the ratio of their perimeters.c) Find the ratio of their areas.
2. Two similar figures have a scale factor of 2 : 5. If the larger figure has a perimeter of 40 ft, what is the perimeter of the smaller figure?
Warm-Up
15 yd
24 yd
Scale DrawingsTarget:
I can use scales for maps, blueprints and models to find missing measurements.
Group Atlas ActivityAs a group:
1.pick a map in the atlas from a time period you are studying or have already studied in social studies (must be a map with a scale).
2.Get familiar with the scale. How many kilometers or miles are represented by 1 inch?
3.Decide on a trip you would like to take within your chosen map. What city would you like to start at? What city do you want to end at?
4.Using your scale, figure out how many miles (or kilometers) the actual distance would be.
Alan’s map has a scale of 2 inches : 5 miles.
The distance on the map from Mt. Hood Meadows to Alan’s home is 16 inches. What is the actual distance?
Write a proportion.
Use cross products to solve. 2x = 80 x = 40
The actual distance is 40 miles.
Example 1a
miles
inches 16
miles 5
inches 2
x
Alan’s map has a scale of 2 inches : 5 miles.
The actual distance from Alan’s home to Portland is 25 miles. Find the distance on the map.
Write a proportion.
Use cross products to solve. 5x = 50 x = 10
The distance to Portland on the map is 10 inches.
Example 1b
miles 25
inches
miles 5
inches 2 x
A model car is made with a scale factor of 1 inch: 11 inches or 1 : 11. The actual car is 7 feet 4 inches long. How long is the model car?
Convert 7 feet 4 inches to inches to 7 ft 4 in = 7·12 + 4 match the scale factor: = 84 + 4 = 88 in
Write a proportion using the scale factor 1 : 11.
Use cross products to solve. 11x = 88 x = 8
The model car is 8 inches long.
Example 2
8811
1 x
Trains!Mrs. Drake’s dad used to be the Vice President of the Portland and Western Railroad. He used to drive a lot of trains like the one below. For his birthday, she’d like to make a scale model of this engine. If the scale she wants to use is 1:52 and the actual engine is 65 feet long, how many inches long will her model need to be?
When have you or a member of your family used a scale drawing? What information did it help you figure out?
Communication Prompt
A map has a scale of 2 inches : 5 miles. Use the given distance on a map to find the actual distance.
1. 8 in
2. 1 ft 2 in
A model car has a scale of 1 : 24.
3. The model car is 4 inches long. How long is the actual car in inches? How long in feet?
Exit ProblemsHomework:Lesson 7.7 Pg. 514-516 #1-3, 5-9, 16, 17, 19, and 21