lesson 19 computing actual areas from a scale drawing

Lesson 19Computing Actual Areas from a Scale

Drawing

Review

What is the difference between scale and scale factor?

Examples 1–3: Exploring Area Relationships

Use the diagrams below to find the scale factor and then find the area of each figure.

Example 1

Scale factor: _________ Actual Area = ______________   Scale Drawing Area = ________________ Ratio of Scale Drawing Area to Actual Area: _________

Example 2

Scale factor: _________

Actual Area = ______________   Scale Drawing Area = ________________ Ratio of Scale Drawing Area to Actual Area: _________

Example 3

Scale factor: _________ Actual Area = ______________   Scale Drawing Area = ________________ Ratio of Scale Drawing Area to Actual Area: _________ 

Why do you think it is squared as opposed to cubed or something else?

How might you use this information I working with scale drawings?

Suppose a rectangle has an area of 12 square m. If it is enlarged by a scale factor of three, what area would you predict the enlarged rectangle to have based on what you just concluded?