Student Resources—746

Make and Use Graphs
Data in tables can be displayed in a
graph—a visual representation of data.
Common graph types include line graphs,
bar graphs, and circle graphs.
Line Graph A line graph shows a relationship
between two variables that change
continuously. The independent variable
is changed and is plotted on the x-axis.
The dependent variable is observed, and
is plotted on the y-axis.
Example Draw a line graph of the data below from
a cyclist in a long-distance race.
Table 5 Bicycle Race Data
Time (h) Distance (km)
0 0
1 8
2 16
3 24
4 32
5 40
Step 1 Determine the x-axis and y-axis variables.
Time varies independently of distance and is
plotted on the x-axis. Distance is dependent
on time and is plotted on the y-axis.
Step 2 Determine the scale of each axis.The x-axis
data ranges from 0 to 5.The y-axis data
ranges from 0 to 40.
Step 3 Using graph paper, draw and label the axes.
Include units in the labels.
Step 4 Draw a point at the intersection of the time
value on the x-axis and corresponding distance
value on the y-axis. Connect the points
and label the graph with a title, as shown in
Figure 20.
Math Skill Handbook
Distance (km)
50
40
30
20
10
Distance v. Time
0 1 2 3 4 5
Time (h)
Figure 20 This line graph shows the relationship
between distance and time during a bicycle ride.
Practice Problem A puppy’s shoulder height is
measured during the first year of her life.The following
measurements were collected: (3 mo, 52 cm),
(6 mo, 72 cm), (9 mo, 83 cm), (12 mo, 86 cm). Graph
this data.
Find a Slope The slope of a straight line is
the ratio of the vertical change, rise, to the
horizontal change, run.
vertical change (rise) ch
Slope ange
in
y
horizontal change (run)
change
in
x
Example Find the slope of the graph in Figure 20.
Step 1 You know that the slope is the change in y
divided by the change in x.
Slope change
in
y
change
in
x
Step 2 Determine the data points you will be using.
For a straight line, choose the two sets of
points that are the farthest apart.
Slope (40–
0)
km
(5–
0)
hr
Step 3 Find the change in y and x.
Slope 40 km
5h
Step 4 Divide the change in y by the change in x.
Slope 8km
h
The slope of the graph is 8 km/h.
MATH SKILL HANDBOOK 789
Math Skill Handbook