7th Grade Math

Chapter Study Guide and Review 421

Variation

PSI: Use a Graph (Lesson 3B)

STATUES For Exercises 24 and 25, use the

graph that shows the heights of four

freestanding statues in the world.

Height (m)

50

0

World’s Statues

100

150

200

Crazy Horse

(USA)Buddah(Japan)

Motherland(Russia)

Indian Rope Trick

(Sweden)

24. Which statue is the tallest?


25. Compare the heights of the Motherland
    statue and the Crazy Horse statue.

EXAMPLE 5 In the graph below, which

place was favored by most students?

Number ofStudents

10

15

5

0

Favorite Vacation Places

CityCruiseCountryBeach

The beach was favored by 12 students,

which was the greatest number.

Direct Variation (Lesson 3C)

Determine whether the linear function is a

direct variation. If so, state the constant of

variation.

26. Tickets Available 80 60 40 20
    Tickets Sold 40 30 20 10


27. Distance (mi) 1,000 2,000 3,000 4,000
    Time (h) 2468

EXAMPLE 6 Determine whether the

linear function is a direct variation. If so,

state the constant of variation.

Number of Iron

Weights^12345

Total Weight (lb) 5 10152025

Since the ratios

total weight

__

number of weights

are all _^5

1

,

the function is a direct variation.

Inverse Variation (Lesson 3E)

28. DRIVING The time it takes to complete a
    driving course varies inversely with the
    speed at which you drive. A driver can
    run the course in 2 hours at an average
    rate of 55 miles per hour. How long
    will it take to drive the same course at
    50 miles per hour?

EXAMPLE 7 The time it takes to read a

book varies inversely with the speed at

which you are reading. Suppose it took

6 days to read a book at a rate of 35 pages

per day. How long will it take to read the

same book at 40 pages per day?

xy = k y = _kx

(6) · (35) = k y = _^21040

210 = k y = 5 _ 41 days

Lesson 3

EXAMPLE 7

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