7th Grade Math

R18 Selected Answers and Solutions

Selected Answers and Solutions

9. x 60 xy

560 · 5 300

10 60 · 10 600

15 60 · 15 900

20 60 · 20 1,200

Domain: {5, 10, 15, 20};

Range: {300, 600, 900, 1,200}

11a. t = 35 m 11b. 525 times; Sample answer:

Replace m with 15 in the equation t = 35 m to fi nd

the number of times a cricket will have chirped

after 15 minutes at this temperature.

13. x 1.3xy

1 1.3 × 1 1.3

2 1.3 × 2 2.6

3 1.3 × 3 3.9

4 1.3 × 4 5.2

Domain: {0, 1, 2, 3};

Range: {1.3, 2.6, 3.9, 5.2}

15.

x 2 _ 3 xy

2 _^23 ×^21 _^13

3 _^23 ×^32

4 _^23 ×^42 _^23

5 _^23 ×^53 _^13

Domain: {2, 3, 4, 5};

Range:

⎧

⎨

⎩

1 ^13 , 2, 2 32 , 3 _ 31

⎫

⎬

⎭

1717 a. Use the distance formula, D = rt to write the

equation. The rate is 8, the distance is m, and the

time is s. Therefore, the equation is m = 8 s.

b. Use the distance formula, D = rt to write the

equation. The rate is 19, the distance is m and the

time is s. Therefore, the equation is m = 19 s.

c. 480 mi; 1,140 mi; Sample answer: Replace s with

60 in the equation m = 8 s and in the equation

m = 19 s to fi nd the number of miles Jupiter

travels in 1 minute and the number of miles

Earth travels in 1 minute, respectively.

19. Divya added 3 to each input rather than
    multiplying by 3. The range should be {6, 12, 18, 24}.
    21a. y = 0.25x 21b. 2.5; 3; 3.5 23. Sample answer:
    You start with an input number, perform the
    operations in the function rule, and the result is the
    output number. 25. G 27. function; Sample
    answer: each element of the domain is paired with
    exactly one element of the range 29. not a
    function; Sample answer: the domain value 12 is
    paired with two range values 4 and 16 31. not a
    function; Sample answer: the graph does not pass
    the vertical line test 33. - 100


20. xf(x) = x - 3 f(x)

22 - 3 - 1

44 - 31

66 - 33

88 - 35

37. xf(x) = 2 x + 6 f(x)

02(-1) + 6 6

1 2(1) + 6 8

3 2(3) + 612

5 2(5) + 616

39. 
    
    
    
    • 100
    
    
    
    

Pages 388–389 Lesson 7-1C

1.

2

0 1

4

6

8

10

12

14

16

Number of Baseballs

Total Cost ($)

Total Cost of Baseballs

234

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

the input x. For example, try 2, 1, 0, and -1.

Substitute these values for x to fi nd the output y.

Graph the points, and draw a line through the

points.

xx - 1 y (x, y)

• 1 - 1 - 1 - 2(-1, -2)
  00 - 1 - 1 (0, -1)
  11 - 1 0 (1, 0)
  22 - 1 1 (2, 1)

y

O x

y = x - 1

5. y

O x

y = - 2 x + 3

R01_R42_EM_SelAns_895130.indd R18 1/18/10 9:51 AM