# Illustrative Mathematics Grade 7, Unit 1, Lesson 9: Creating Scale Drawings

Learning Targets:

• I can determine the scale of a scale drawing when I know lengths on the drawing and corresponding actual lengths.
• I know how different scales affect the lengths in the scale drawing.
• When I know the actual measurements, I can create a scale drawing at a given scale.

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Illustrative Math

#### Lesson 9: Creating Scale Drawings

Let’s create our own scale drawings.

Illustrative Math Unit 7.1, Lesson 9 (printable worksheets)

#### Lesson 9 Summary

The following diagram shows how different scales affect the lengths in the scale drawing.

#### Lesson 9.1 Number Talk: Which is Greater?

Without calculating, decide which quotient is larger.
11 ÷ 23 or 7 ÷ 13
0.63 ÷ 2 or 0.55 ÷ 3
15 ÷ 1/3 or 15 ÷ 1/4

#### Lesson 9.2 Bedroom Floor Plan

Noah made a rough sketch of the layout of his room (not a scale drawing).

1. Noah wants to create a floor plan that is a scale drawing. The actual length of Wall C is 4 m. Noah draws a segment 16 cm long to represent Wall C. What scale is he using? Explain or show your reasoning.
2. Find another way to express the scale.
3. Pause and discuss your responses with a partner. How do your scales compare?
4. The actual lengths of Wall A, Wall B, and Wall D are 2.5 m, 2.75 m, and 3.75 m. Determine how long these walls will be on Noah’s scale floor plan.
5. Use the Point tool and the Segment tool and the Segment tool
Open Applet

#### Are you ready for more?

Jada finds a map that says, “Note: This map is not to scale.” What do you think this means? Why is this information important?

Not to scale means we cannot use the distances on the map to find the actual distances between locations.

#### Lesson 9.3 Two Maps of Utah

A rectangle around Utah is about 270 miles wide and about 350 miles tall. The upper right corner that is missing is about 110 miles wide and about 70 miles tall.
Make a scale drawing of Utah where 1 centimeter represents 50 miles.
Make a scale drawing of Utah where 1 centimeter represents 75 miles.
How do the two drawings compare? How does the choice of scale influence the drawing?

#### Lesson 9 Practice Problems

1. An image of a book shown on a website is 1.5 inches wide and 3 inches tall on a computer monitor. The actual book is 9 inches wide. a. What scale is being used for the image? b. How tall is the actual book?
2. The flag of Colombia is a rectangle that is 6 ft long with three horizontal strips.
The top stripe is 2 ft tall and is yellow.
The middle stripe is 1 ft tall and is blue.
The bottom stripe is also 1 ft tall and is red.
a. Create a scale drawing of the Colombian flag with a scale of 1 cm to 2 ft.
b. Create a scale drawing of the Colombian flag with a scale of 2 cm to 1 ft.
3. These triangles are scaled copies of each other.
For each pair of triangles listed, the area of the second triangle is how many times larger than the area of the first?
a. Triangle G and Triangle F
b. Triangle G and Triangle B
c. Triangle B and Triangle F
d. Triangle F and Triangle H
e. Triangle G and Triangle H
f. Triangle H and Triangle B
4. Here is an unlabeled rectangle, followed by other quadrilaterals that are labeled.
a. Select all quadrilaterals that are scaled copies of the unlabeled rectangle. Explain how you know.
b. On graph paper, draw a different scaled version of the original rectangle.

The Open Up Resources math curriculum is free to download from the Open Up Resources website and is also available from Illustrative Mathematics.

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