8-3 Proportions and Customary Measurement

Course 1

Warm UpWarm Up

Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

Warm UpFind the missing value in each proportion.

1. =

2. =

3. =

4. =

x = 6

x = 25

x = 35

Course 1

8-3 Proportions and Customary Measurement

4 1

__ 24 x

__

x30

__ 5 6

__

1416

__ x 40

__

8 x

__ 12 18

__ x = 12

Problem of the Day

There are 4 ounces in a gill. There are 4 gills in a pint. There are 8 pints in a gallon. How many ounces are the same as the total of 3 gallons, 3 pints, 3 gills, and 3 ounces?447

Course 1

8-3 Proportions and Customary Measurement

Learn to use proportions to make conversions within the customary system.

Course 1

8-3 Proportions and Customary Measurement

Course 1

8-3 Proportions and Customary Measurement

Additional Example 1A: Using Proportions to Convert Measurements

A. Sonja went hiking for 4 hours. For how many minutes did she go hiking?

4 hrx min

____ 1 hr60 min

_____ =

1 hour is 60 minutes. Write a proportion. Use a variable for the value you are trying to find.

The cross products are equal.60 • 4 = 1 • x

240 = x

Sonja hiked for 240 minutes.

Course 1

8-3 Proportions and Customary Measurement

Additional Example 1B: Using Proportions to Convert Measurements

B. Mr. Lee is 72 inches tall. Find his height in feet.

x ft72 in.

____ 1 ft 12 in

____ =

1 foot is 12 inches. Write a proportion. Use a variable for the value you are trying to find.The cross products are equal.12 • x = 1 • 72

x is multiplied by 12.12x = 72

Mr. Lee is 6 feet tall.

12x 12

___ 72 12

___ = Divide both sides by 12 to undo the multiplication.

x = 6

Course 1

8-3 Proportions and Customary Measurement

Additional Example 1C: Using Proportions to Convert Measurements

C. Hunter used 56 cups of water to wash his car. How many gallons of water did he use?

x gal56 cups

______ 1 gal 16 cups

_______ =1 gallon is 16 cups. Write a proportion. Use a variable for the value you are trying to find.

The cross products are equal.16 • x = 1 • 56

x is multiplied by 16.16x = 56

Hunter used 3.5 gallons of water to wash his car.

16x 16

___ 56 16

___ = Divide both sides by 16 to undo the multiplication.

x = 3.5

Course 1

8-3 Proportions and Customary Measurement

Try This: Example 1A

A. Helga went biking for 3 hours. For how many minutes did she go biking?

3 hrx min

____ 1 hr60 min

_____ =

1 hour is 60 minutes. Write a proportion. Use a variable for the value you are trying to find.

The cross products are equal.60 • 3 = 1 • x

180 = x

Helga biked for 180 minutes.

Course 1

8-3 Proportions and Customary Measurement

Try This: Example 1B

B. Ms. Hagan is 60 inches tall. Find her height in feet.

x ft60 in.

____ 1 ft 12 in.

____ =

1 foot is 12 inches. Write a proportion. Use a variable for the value you are trying to find.

The cross products are equal.12 • x = 1 • 60

x is multiplied by 12.12x = 60

Ms. Hagan is 5 feet tall.

12x 12

___ 60 12

___ = Divide both sides by 12 to undo the multiplication.

x = 5

Course 1

8-3 Proportions and Customary Measurement

Try This: Example 1C

C. Seymour used 40 cups of water to wash his dog. How many gallons of water did he use?

x gal40 cups

______ 1 gal 16 cups

_______ =1 gallon is 16 cups. Write a proportion. Use a variable for the value you are trying to find.

The cross products are equal.16 • x = 1 • 40

x is multiplied by 16.16x = 40

Seymour used 2.5 gallons of water to wash his dog.

16x 16

___ 40 16

___ = Divide both sides by 16 to undo the multiplication.

x = 2.5

Course 1

8-3 Proportions and Customary Measurement

Lesson Quiz

Find the missing value.

1. in. = 6 yd

2. 24 pt = gal

Compare. Write <, >, or =.

3. 42 oz 2 lb.

4. 7,920 ft 1.5 mi

5. If your family is going to take a 3-week

vacation, how many days will you be gone?

3

216

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21 daysCourse 1

8-3 Proportions and Customary Measurement