7th Grade Math

Lesson 1C Rates and Functions 387

SWIMMING Michael Phelps swims the 400-meter individual

medley at an average speed of 100 meters per minute. The

equation d = 100 t describes the distance d that he can swim in

t minutes at this speed. Represent the function by a graph.

Step 1 Select any four values t 100 t d (t, d )

1 100(1) 100 (1, 100)

2 100(2) 200 (2, 200)

3 100(3) 300 (3, 300)

4 100(4) 400 (4, 400)

for t. Select only

positive numbers

because t represents

time. Make a function

table.

Step 2 Graph the ordered pairs and draw a line through the

points.

Distance (m)

0 12345

Time (min)

(1, 100)

(2, 200)

(3, 300)

(4, 400)

Swimming

450

400

350

300

250

200

150

100

50

e. JOBS Sandi makes $6 an hour babysitting. The equation m = 6 h

describes how much money m she earns babysitting for h hours.

Represent this function by a graph.

Representing Functions

Words There are 12 inches in one foot.

Table Feet (f) Inches (n)

112

224

336

448

Graph Convert Feet to Inches

1

10

20

30

40

50

60

Feet

Inches

Equation n = 12 f, where f represents 0 234

the number of feet and n

represents the number

of inches.

When drawing a graph,

include a title and labels

for the horizontal and

vertical axes.

385_390_C07_L1_895130.indd 387 12/31/09 4:24 PM