Lesson 17

Using Scale Drawings

Scale Drawings

• Scale drawings and scale models make it possible to show objects accurately that are either too large or too small to draw to their actual size.

• A scale is given that relates the dimensions of the drawing or model to the dimensions of the actual objects.

Some examples

• Common examples of scale drawings are maps, architects’ blueprints, and models of buildings.

• A scale drawing is similar to the object it represents.

Example 1

• Mr. Dunham made this scale drawing of a turtle that he once observed. In the drawing, the length of the turtle’s shell in 15 mm. What was the actual length of the shell of the turtle Mr. Dunham observed?

Scale:5mm=10cm

15mm

What is the strategy?

• Write a ratio to represent the scale– The scale is 5mm = 10cm, which can be written

5mm: 10cm– Write a ratio comparing the drawing length to

actual length, 15mm: s– Set up a proportion and solve for s. – S=30– The actual length of the turtle’s shell was 30

centimeters.

Example 2

• On a map. Kristin measured the straight line distance between Hoboken and Camden to be 5 inches. The scale on the map shows that ¼ inch = 4 miles. What is the actual distance between Hoboken and Camden?– What strategy would you use?– Write a ratio to represent the scale. ¼ / 4– Set up the proportion and solve.– The actual distance is 80 miles.

Practice

• Look at pg 109 in the Coach book. Work on your own to complete 1-6. The partner up to compare your answers and work on the open ended.