Math 6/7 NOTES (7.1) Name Proportions (SOL 7.4)

Math 6/7 NOTES (7.1)

Name ______________________________

Proportions (SOL 7.4)

When two ratios are ___________________, they form a proportion.

In a proportion, a ______________________________ is the product of the numerator of one ratio and the denominator of the other ratio. We can use cross-products to identify proportions!

1=3

26

=

Examples: Determine whether each pair of ratios forms a proportion.

4)

6, 3

10 5

6)

1.2, 2

4.0 5

5)

1, 3

39

7)

12, 2

24 6

Solving a Proportion:

You can use cross products to find a missing term in a proportion.

Cross multiply

1 =

5 60

10 = 2.5

4

Set-up the equation

Solve the equation

You Try!

8)

= 52

25 100

9)

= 3

35 7

10)

12.5 = 15

7.5

11)

3 = 18

24

!!!!! KEEP the units of measurement in the same place on each ratio !!!!

Ex. An 8-ounce glass of orange juice contains 72 milligrams of vitamin C. How much juice contains 60 milligrams of vitamin C?

Ex. The skull length of a crocodile is proportional to its body length. In one species, a 6-foot crocodile has a 2-foot skull. Estimate the length of a crocodile of that species that has a 3.5-foot skull.

1. A 12-ounce bottle of shampoo lasts Enrique 16 weeks. How long would you expect an 18-ounce bottle of the same brand to last him?

2. About 13 out of 20 homes have a personal computer. On a street with 60 homes, how many would you expect to have a personal computer?

3. A 6-ounce package of fruit snacks contains 45 pieces. How many pieces would you expect in a 10-ounce package?

4. Ingrid types 3 pages in the same amount of time that Tanya types 4.5 pages. If Ingrid and Tanya start typing at the same time, how many pages will Tanya have typed when Ingrid has typed 11 pages?

5. A grading machine can grade 48 multiple-choice tests in 1 minute. How long will it take the machine to grade 300 tests?

6. The waiting time to ride a roller coaster is 20 minutes when 150 people are in line. How long is the waiting time when 240 people are in line?

Math 6/7 Homework (7.1)

Name ______________________________

Do the ratios form a proportion? Show your work. Write yes or no.

7

5

1)

9 and 7

4

10

2)

11 and 27.5

8

12

3) 24 and 28

20

30

4)

and

35

45

7

49

5)

and

9

63

4

12

6)

and

7

71

Solve each proportion by creating an equation. Show your work.

7)

5 15

=

7

7

8)

=

12 42

82

9)

=

5

Write a proportion for each problem. Then solve. Round to the nearest tenth if necessary.

10) There are 90 books on 5 shelves, how many books are there on 14 shelves?

11) You pay $18.00 for 30 text messages. At the same rate, how much would 12 text messages cost?

12) Of the 50 fish that Jim caught from the lake, 14 were trout. The estimated population of the lake is 7,500 fish. About how many trout would you expect to be in the lake?

13) A shop produces 39 wetsuits every 2 weeks. How long will it take the shop to produce 429 wetsuits?

NAME ________________________________________ DATE ______________ PERIOD _____

Practice: Word Problems

Solving Proportions

1. COOKING Theo wants to use a cookie recipe that makes 36 cookies but he wants to reduce the number of cookies to 24. If the recipe specifies using 2 cups of sugar, how much sugar should he use?

2. MEDICINE In order to determine her pulse rate, June's nurse counted 18 beats in her pulse in 15 seconds. At this rate, how many beats would she have in 60 seconds?

3. LABOR Ed earned $112 for 8 hours of work. At this rate, how much will he earn for 40 hours of work?

4. TRAVEL Rita traveled 1,250 miles in the first 3 days of her trip. At this rate, how long will it take her to travel 1,875 miles?

412 days

5. MODELS An architect built a model of a 220-foot tall building he is designing. The model is 25 inches tall and 10 inches wide. How wide is the actual building?

6. TESTING Mary is preparing for her college entrance exams. In a practice test, she answered 12 problems in 30 minutes. At this rate, how many questions can she expect to answer in 150 minutes?

Lesson 7?3

? Glencoe/McGraw-Hill

387 Mathematics: Applications and Concepts, Course 2

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