Proportions and Scale Drawings

Textbook Pages 430-435

Objective

• I can solve scale drawing problems using proportions.

Vocabulary

• • Scale Drawing: is the same shape but not the same size. A map is a scale drawing. The units are very important.

Scale: tells us how the drawings dimensions and the actual dimensions are related. (Ratio) • The standard way to write the scale is scale model to actual object or scale:actual

Interpreting Scale Drawing

• 3 inches • • The scale is 1 in. : 5ft Find the actual length of the canoe.

• 1in 5ft 3 in.

?ft

What did you do to 1 to get to 3. Multiplied by 3. So multiply 5 by 3 to get 15 ft.

• • • Try some!

The scale of a drawing 2 in.: 6m Length of the drawing = 8in.

Length of object = __________ • • Length of object = 36 m Length of drawing = __________

Word Problems

You are building a model boat with a scale of 1 in.:2ft. The actual boat is 18 feet long. How long should you make your model?

9 inches

Using it to find area and perimeter.

• A scale drawing of this classroom is 2cm by 3 cm. The scale is 1cm:2m. What is the area of the classroom?

• •

Draw a diagram

Using the scale model 1in.:10ft, make a scale drawing of a 30ft by 40 foot dance floor. You should have a 3in by 4 in drawing • • • Use your drawing to find the actual distance from opposite corners. If you measured on your scale drawing you would find it to be 5 inches.

Using the scale it would convert to 50 ft.

Finding the scale!

• A museum is creating a full sized T-Rex from a model. The model is 40 inches in length. The resulting dinosaur will be 40 feet tall in length. What is the models scale?

• Write a ratio. Make sure both measures are in inches. Then simplify.

• 40in = 40 in 40 ft 480 in The model scale is 1:12

Try some:

• • Find the model scale: 5in 2ft 5/24 1ft 8yd 1/24

Practice

• Workbook Pages 109-110 Even