# 10. Areas of scale drawings relate by the square of the scale factor (A)

teaches Common Core State Standards CCSS.Math.Content.7.G.A.1 http://corestandards.org/Math/Content/7/G/A/1
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3

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Lesson objective: Apply scale factors to dimensions, perimeter and area.

This lesson provides an opportunity for students to apply their knowledge and understanding of scale drawings to a real-life situation. Students are asked to reason about mathematical statements dealing with the relationship between scaled figures.

Key Concept students will use:

• Scale drawings may be larger, smaller, or the same size as an original drawing.

• Lengths of sides of pairs of scale drawings are proportional, resulting in proportional perimeters.

• Areas of pairs of scaled figures are related by the square of the scale factor.

Skills students will use:

• Calculate dimensions of a scaled figure.
• Calculate perimeter of a scaled figure using the scale factor and the perimeter of the original.
• Calculate area of a scaled figure by finding the product of the square of the scale factor and the original area.

Students engage in Mathematical Practice 3 (Construct viable arguments and critique the reasoning of others) as they explain why Diego's statements are or are not correct and justify their corrections.

Key vocabulary:

• Exponents
• Original figure
• Powers
• Proportions
• Ratios
• Scale drawings
• Scale factor
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