Scale Factors and Area Ratios

This video tutorial covers lesson 19 for grade seven, focusing on computing actual areas from scale drawings. It includes examples with rectangles and triangles to demonstrate how to calculate scale factors and the ratio of scale drawing areas to actual areas. The video concludes with observations on the relationship between scale factors and area ratios, emphasizing that the area ratio is the square of the scale factor. An application example using a basketball court is also provided.

What is the main focus of lesson 19 in module 1 for grade seven?

• Exploring geometric shapes

• Learning about volume calculations

• Computing actual areas from scale drawings

• Understanding scale dimensions

In example 1, what is the scale factor for the rectangles?

• 3

• 2

• 1/2

• 4

What is the value of the ratio of the scale drawing area to the actual area in example 1?

• 5

• 4

• 3

• 2

In example 2, what is the scale factor when the actual picture is larger than the scale drawing?

• 3/4

• 1/3

• 1/2

• 2/3

What is the value of the ratio of the scale drawing area to the actual area in example 2?

• 1/9

• 1/3

• 1/12

• 1/6

In example 3, what is the scale factor for the triangle?

• 2/3

• 3/4

• 4/3

• 5/3

What is the value of the ratio of the scale drawing area to the actual area in example 3?

• 4/3

• 3/4

• 16/9

• 9/16

What conclusion can be drawn about the relationship between scale factor and area ratio?

• The area ratio is the cube of the scale factor

• The area ratio is the square of the scale factor

• The area ratio is half of the scale factor

• The area ratio is double the scale factor

In example 4, what is the scale factor used for the basketball court?

• 1/15

• 1/20

• 1/25

• 1/10

What is the actual area of the basketball court in example 4?

• 500 square ft

• 600 square ft

• 750 square ft

• 900 square ft