7th Grade Math

Test PracticeT

410 Linear Functions

24. To make lemonade, Andy adds
    8 tablespoons of sugar for every
    12 ounces of water. If he uses
    32 ounces of water, which proportion
    can he use to find the number of
    tablespoons of sugar x he should add
    to make the lemonade?
    A. 128 = ^32 x C. 128 = 32 x

B. x^8 = 1232 D. 12 x = 328

25. Anjuli read 22 pages during a 30-minute
    study hall. At this rate, how many pages
    would she read in 45 minutes?
    F. 30
    G. 33
    H. 45
    I. 48

Graphing Linear Equations

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Some situations start with a given amount and increase at a certain rate. For

example, in Example 2, pizzas cost $8 each with a $3 delivery charge. The

equation y = 8 x + 3 represents the total cost y of x pizzas.

Equations such as y = 8 x + 3 are written in the form y = mx + b, where m is

the slope and b is the y-intercept. It is called slope-intercept form.

slope y = mx + b

y-intercept, the y-coordinate of the point

where the graph crosses the x-axis

y = 8 x + 3

The slope is 8 or _^81. This means the cost is

$8 per pizza.

The y-intercept is at (0, 3). This means the

delivery charge is $3.

To find the total cost of 6 pizzas, replace

x with 6. Since 8(6) + 3 = 51, six pizzas

cost $51.

ROAD TRIP On Day 1, the Lopez family drove 100 miles. On Day 2, they

drove x hours at 45 miles per hour.

26. Write and graph an equation for the total distance the Lopez family
    drove by the end of Day 2.


27. Interpret the meaning of the slope and y-intercept for your equation.


28. If the Lopez family drove 6 hours on Day 2, how many miles did they
    drive altogether? Show how you solved.


29. Does your equation show a proportional relationship? Explain.

Charge ($)

12345678

Number of Pizzas

0

10

20

30

40

50

60

(1, 11)

(2, 19)

(3, 27)

(4, 35)

Pizza Delivery Cost

404_415_C07_L3_895130.indd 410 12/31/09 4:33 PM