7th Grade Math

Selected Answers and Solutions R19

Selected Answers and Solutions

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7. Phone Bill

1234

10.05

10

9.95

10.1

10.15

10.2

Total ($)

10.25

10.3

Time (h)

0

9. 
   
   
   
   11. y
   
   
   
   

O x

y = x + 1

y

O x

y = x

13. 
    
    
    
    15. y
    
    
    
    

O x

y = 2 x + 3

24

01234

48

72

96

120

144

g

m

Gasoline (gal)

Distance (mi)

Gas Mileage

17. y

y = 0.25x

0 x

1919 Graph y = 0.5x - 1. Select any four values for

the input x. We chose 4, 2, 0, and -2 in order to

have whole number values for y. Substitute these

values for x to fi nd the output y. Graph the points,

and draw a line through the points.

x 0.5x - 1 y (x, y)

• 2 0.5(-2) - 1 - 2(-2, -2)
  0 0.5(0) - 1 - 1 (0, -1)
  2 0.5(2) - 1 0 (2, 0)
  4 0.5(4) - 1 1 (4, 1)

y = 0.5x - 1

y

x

0

23. Sample answer: {(1, 2), (1, 3), (2, 4)}; This set is
    not a function because 1 is mapped to two y-values,
    2 and 3. 25. F

Pages 393–395 Lesson 7-2B

11 Find the unit rate to determine the constant

rate of change.

change in temperature

__change in time = _2 hours3°F

= _1 hour1.5°F

So, the temperature rises by 1.5°F per hour.

3. 6 m per s 5. about $0.03 per min
   77 To fi nd the rate of change, pick any two points
   on the line, such as (18, 216) and (6, 72).
   change in length
   change in height =
   (216 - 72) inches
   (18 - 6) inches

= 144 inches_12 inches or 12 inches_1 inch

The length increases 12 inches for every inch the

height increases. So, the rate of change is 12 inches

of length per inch of height.

99 a. Write and solve a proportion to determine

how many laps equal 1 mile.

20 laps

_5 miles =

x laps

_1 mile

5 x = 20

_^5 5 x = _^205

x = 4

So, 4 laps equal 1 mile. From the information on the

clipboard, it takes Seth 57.1 seconds to complete

4 laps, or 1 mile.

Find the unit rate to determine the constant rate of

change.

change in miles

__change in seconds = __57.1 seconds1 mile

≈ 0.0175 mile_1 second

R01_R42_EM_SelAns_895130.indd R19 1/19/10 11:09 AM