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192 Chapter 5 Ratios and Proportions Slope 5.5 How can you compare two rates graphically? Work with a partner. The table shows the maximum speeds of several animals. a. Find the missing speeds. Round your answers to the nearest tenth. b. Which animal is fastest? Which animal is slowest? c. Explain how you convert between the two units of speed. ACTIVITY: Comparing Unit Rates 1 1 Animal Speed (miles per hour) Speed (feet per second) Antelope 61.0 Black mamba snake 29.3 Cheetah 102.6 Chicken 13.2 Coyote 43.0 Domestic pig 16.0 Elephant 36.6 Elk 66.0 Giant tortoise 0.2 Giraffe 32.0 Gray fox 61.6 Greyhound 39.4 Grizzly bear 44.0 Human 41.0 Hyena 40.0 Jackal 35.0 Lion 73.3 Peregrine falcon 200.0 Quarter horse 47.5 Spider 1.76 Squirrel 12.0 Thomson’s gazelle 50.0 Three-toed sloth 0.2 Tuna 47.0 4 a sn g nake e 4 3 2 4 1 lle 5 h 4 con n Slope In this lesson, you will find the slopes of lines. interpret the slopes of lines as rates.

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192 Chapter 5 Ratios and Proportions

Slope5.5

How can you compare two rates graphically?

Work with a partner. The table shows the maximum speeds of several animals.

a. Find the missing speeds. Round your answers to the nearest tenth.

b. Which animal is fastest? Which animal is slowest?

c. Explain how you convert between the two units of speed.

ACTIVITY: Comparing Unit Rates11

AnimalSpeed

(miles per hour)Speed

(feet per second)

Antelope 61.0

Black mamba snake 29.3

Cheetah 102.6

Chicken 13.2

Coyote 43.0

Domestic pig 16.0

Elephant 36.6

Elk 66.0

Giant tortoise 0.2

Giraffe 32.0

Gray fox 61.6

Greyhound 39.4

Grizzly bear 44.0

Human 41.0

Hyena 40.0

Jackal 35.0

Lion 73.3

Peregrine falcon 200.0

Quarter horse 47.5

Spider 1.76

Squirrel 12.0

Thomson’s gazelle 50.0

Three-toed sloth 0.2

Tuna 47.0

4

a sn

g

nake

e

4

3

2

4

1

lle 5

h

4

conn

SlopeIn this lesson, you will● fi nd the slopes of lines.● interpret the slopes of

lines as rates.

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Section 5.5 Slope 193

Work with a partner. A cheetah and a Thomson’s gazelle run at maximum speed.

a. Use the table in Activity 1 to calculate the missing distances.

Cheetah Gazelle

Time (seconds) Distance (feet) Distance (feet)

0

1

2

3

4

5

6

7

b. Use the table to write ordered pairs. Then plot the ordered pairs and connect the points for each animal. What do you notice about the graphs?

c. Which graph is steeper? The speed of which animal is greater?

ACTIVITY: Comparing Two Rates Graphically22

3. IN YOUR OWN WORDS How can you compare two rates graphically? Explain your reasoning. Give some examples with your answer.

4. REPEATED REASONING Choose 10 animals from Activity 1.

a. Make a table for each animal similar to the table in Activity 2.

b. Sketch a graph of the distances for each animal.

c. Compare the steepness of the 10 graphs. What can you conclude?

ater?

00

100

200

300

400

500

600

700

1 2

Time (seconds)

Dis

tan

ce (f

eet)

3 4 5 6 7 x

y

ApplyMathematicsHow can you use the graph to determine which animal has the greater speed?

Math Practice

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194 Chapter 5 Ratios and Proportions

Lesson5.5

Key Vocabularyslope, p. 194

Slope

Slope is the rate of change between any

x

y

1 2 3 4 5 6 7

1

2

3

4

5

6

7

Slope

3

2 32

two points on a line. It is a measure of the steepness of a line.

To fi nd the slope of a line, fi nd the ratio of the change in y (vertical change) to the change in x (horizontal change).

slope = change in y

— change in x

Find the slope of each line.

a.

x

y

43 5

(0, 0)

(3, 4)

3

4

5

2

3

4

b. y

x

2

2

3

2 3 4

( 2, 2)

(4, 1)

3

6

slope = change in y

— change in x

slope = change in y

— change in x

= 4

— 3

= 3

— 6

= 1

— 2

The slope of the line is 4

— 3

. The slope of the line is 1

— 2

.

Find the slope of the line.

1.

x

y

1

2

3

4

3 4 51

2

(0, 0)

(5, 2)

2.

x

y

1 2 3 4

4

6

8

10

12

(1, 5)

(2, 8)

2

EXAMPLE Finding Slopes11

Exercises 4 – 9

Lesson Tutorials

Study TipThe slope of a line is the same between any two points on the line because lines have a constant rate of change.

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Section 5.5 Slope 195

The table shows your earnings for babysitting.

a. Graph the data.

b. Find and interpret the slope of the line through the points.

Hours, x 0 2 4 6 8 10

Earnings, y (dollars)

0 10 20 30 40 50

a. Graph the data. Draw a line through the points.

b. Choose any two points to fi nd the slope of the line.

slope = change in y

— change in x

= 20

— 4

= 5

The slope of the line represents the unit rate. The slope is 5. So, you earn $5 per hour babysitting.

3. In Example 2, use two other points to fi nd the slope. Does the slope change?

4. The graph shows the amounts you and your friend earn babysitting.

x

y

10

20

30

40

50

60

2 4 6 8 10

Earn

ing

s (d

olla

rs)

Hours

Babysitting

YouFriend

(4, 28)

(8, 56)

(4, 20)

(8, 40)

1 3 5 7 90

0

a. Compare the steepness of the lines. What does this mean in the context of the problem?

b. Find and interpret the slope of the blue line.

EXAMPLE Interpreting a Slope22

dollars

hours

Exercises 10 and 11

x

y

10

20

30

40

50

60

2 4 6 8 10

Earn

ing

s (d

olla

rs)

Hours

Babysitting

(8, 40)

(4, 20)4

20

1 3 5 7 900

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196 Chapter 5 Ratios and Proportions

Exercises5.5

1. VOCABULARY Is there a connection between rate and slope? Explain.

2. REASONING Which line has the greatest slope?

x

y

1

2

3

4

1 2 3 4 5

A B

C 3. REASONING Is it more diffi cult to run up a ramp with

a slope of 1

— 5

or a ramp with a slope of 5? Explain.

9+(-6)=3

3+(-3)=

4+(-9)=

9+(-1)=

Find the slope of the line.

4.

x

y

3 4

4

3

2

1

5

(1, 4)

(0, 0)

5.

x

y

3 4

4

3

2

1

5

(2, 3)

(0, 0)

6.

x

y

3

4

2

4321 5 6

5

(3, 2)(6, 3)

7.

x

y4

2

1

12 145

(1, 4)

( 4, 1)

8.

x

y3

2

1

21234

(2, 1.5)

( 4, 3)

2

9.

x

y

2

4 6 8 10

4

6

8

(4, 1.2)

(10, 6)

2

Graph the data. Then fi nd and interpret the slope of the line through the points.

10. Minutes, x 3 5 7 9

Words, y 135 225 315 405

11. Gallons, x 5 10 15 20

Miles, y 162.5 325 487.5 650

12. ERROR ANALYSIS Describe and correct the error in fi nding the slope of the line passing through (0, 0) and (4, 5).

11

22

slope = 4 — 5

x

y

431 5

2

35

4

4

5(4, 5)

(0, 0)

Help with Homework

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Section 5.5 Slope 197

Multiply. (Section 2.4)

20. − 3

— 5

× 8

— 6

21. 1 1

— 2

× ( − 6

— 15

) 22. − 2 1

— 4

× ( − 1 1

— 3

)

23. MULTIPLE CHOICE You have 18 stamps from Mexico in your stamp collection.

These stamps represent 3

— 8

of your collection. The rest of the stamps are from the

United States. How many stamps are from the United States? (Section 3.4)

○A 12 ○B 24 ○C 30 ○D 48

Graph the line that passes through the two points. Then fi nd the slope of the line.

13. (0, 0), ( 1 — 3

, 7

— 3

) 14. ( − 3

— 2

, − 3

— 2

) , ( 3 — 2

, 3

— 2

) 15. ( 1, 5

— 2

) , ( − 1

— 2

, − 1

— 4

)

16. CAMPING The graph shows the amount

x

y

2 4 6 8 10

Savi

ng

s (d

olla

rs)

Weeks

Camping Trip

40

80

120(5, 100)

(2, 40) (4, 60)

(8, 120)

20

60

100

1 3 5 7 90

0

YouFriend

of money you and a friend are saving for a camping trip.

a. Compare the steepness of the lines. What does this mean in the context of the problem?

b. Find the slope of each line.

c. How much more money does your friend save each week than you?

d. The camping trip costs $165. How long will it take you to save enough money?

17. MAPS An atlas contains a map of Ohio. The table shows data from the key on the map.

Distance on Map (mm), x 10 20 30 40

Actual Distance (mi), y 25 50 75 100

a. Graph the data.

b. Find the slope of the line. What does this mean in the context of the problem?

c. The map distance between Toledo and Columbus is 48 millimeters. What is the actual distance?

d. Cincinnati is about 225 miles from Cleveland. What is the distance between these cities on the map?

18. CRITICAL THINKING What is the slope of a line that passes through the points (2, 0) and (5, 0)? Explain.

19. A line has a slope of 2. It passes through the points (1, 2) and (3, y). What is the value of y ?

Cincinnati

ClevelandToledo

Columbus

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