Using Proportional Relationships

Geometry H2 (Holt 7-5) K. Santos

Tyler wants to find the height of a telephone pole. He measured the pole’s shadow and his own shadow. What is the height of the pole?

Example 1

On a Wisconsin road map, Kristin measured a distance of 11 in from Madison to Wausau. The scale on this map is 1 inch: 13 miles. What is the actual distance between Madison and Wausau to the nearest mile?

Example 2

Lady Liberty holds a tablet in her left hand. The tablet is 7.19 m long and 4.14 m wide. If you made a scale drawing using the scale 1cm: 0.75m, what would be the dimensions to the nearest tenth?

Example 3

If the similarity ratio of two similar figures is , then

The ratio of the perimeters is The ratio of the areas is or

Proportional Perimeters and Areas Theorem (7-

5-1)

In the triangles below, find the similarity ratio, the perimeter ratio and the area ratio.

10 8 4 5

3 6

Similarity ratio:

Perimeter ratio:

Area Perimeter:

Example 1

Two similar pentagons have a scale factor of 2:3. the large pentagon has an area of 24 . Find the area of the smaller pentagon.

Example 2

Given that find the perimeter P and area of has perimeter = 36 cm and area = 60.

M R 9.1 cm

13 cm

Q S L N

Example 3