1. Problem Solving Using Proportions
Chapter 8.3
Problem Solving Using Proportions

2. Objectives I will use proportions to solve real-life problems.
I will use similar triangles to measure objects indirectly.

3. Solving real-life problems
Proportions are used in architecture and manufacturing to construct scale models.
You can also use proportions to find dimensions.

4. Finding Dimensions
You have a scale model of a Boeing The model was built using a 1 – to 250 scale. The wing span on the model is 7 ½ in. What is the wing span of an actual 767?

5. Finding Dimensions Continued
Step 1: Set up a proportion
Step 2: Use Cross Product Property
Step 3: Solve Equation
1875 = x
The wing span of a 767 is 1875 in. Convert this measurement back into feet by dividing by ÷ 12 = 156 ft.

6. Give it a try! 
The scale on a map reads 1 in = 5 mi. Find the actual length of a road that is 2.5 in. long on the map.
Step 1: Set up a proportion
Step 2: Cross Multiply
1x = 12.5
x = miles

7. Finding the height of a building
To estimate the height of the Transco Tower in Huston, Texas, you measure its shadow to be about 55 m. The shadow of a 50 m flagpole is about 10 m. Estimate the height of the Transco Tower.

8. Height of a building Step 1: Set up a proportion:
Transco Tower Height = H
Flagpole Height = h = 50
Transco Tower Shadow = D = 55
Flagpole Shadow = d = 10
Step 2: Cross Multiply and write an equation
H (10) = 50 (55)
10 H = 2750
Step 3: Solve the equation: H = 275
The Transco Tower is about 275 m high.

9. Give it a try! 
A meteorologist reports that the ratio of snowfall in January to total snowfall during the average winter is 2 to 5. If 34 inches have fallen in January of the current year, find the predicted total snowfall for the entire winter.
Proportion: