Lesson 7-8 Graphs
Circle Graphs – used to compare parts of a data set to the whole set of data. The percents
in a circle graph always add up to 100.
If I spin in a circle, I have rotated 360 degrees.
Example 1 Construct a Circle Graph from Percents
RESTAURANTS The table gives the percentages
of favorite restaurants. Construct a circle graph
using the information in the table.
Step 1
There are 360 in a circle. So, multiply each
percent by 360 to find the number of degrees for
each section of the graph.
Chinese:
Italian:
Mexican:
Pizza:
Other:
Favorite Type of
Restaurant
Restaurant
Percent
Chinese
12%
Italian
15%
Mexican
25%
Pizza
40%
Other
8%
12% of 360 = 0.12  360  43
15% of 360 = 0.15  360 = 54
25% of 360 = 0.25  360 = 90
40% of 360 = 0.40  360 = 144
8% of 360 = 0.08  360  29
Step 2 Use a compass to draw a circle and a
radius. Then use a protractor to draw
a 43 angle. This section represents
the number of people who chose
Chinese as their favorite type of
restaurant. From the new radius, draw
the next angle. Repeat for each of the
remaining angles. Label each section.
Then give the graph a title.
Example 2 Construct a Circle Graph from Data
Construct a circle graph using the information in
the table at the right.
Step 1
Find the total number of students.
7 + 11 + 16 + 9 + 5 + 2 = 50
Step 2
Find the ratio that compares the number of
students in each group to the total number
of students.
none: 7  50 = 0.14
one: 11  50 = 0.22
two: 16  50 = 0.32
Favorite Type of
Restaurant
8%
Other
12%
Chinese
40%
Pizza
15%
Italian
25%
Mexican
How Many Pets Do You Have?
Number of
Number of
Pets
Students
none
7
one
11
two
16
three
9
four
5
five or more
2
three:
9  50 = 0.18
four:
5  50 = 0.10
five or more: 2  50 = 0.04
Step 3
Use these ratios to find the number of degrees of each section. Round to the
nearest degree if necessary.
none:
0.14  360 = 50.4 or about 50
one:
0.22  360 = 79.2 or about 79
two:
0.32  360 = 115.2 or about 115
three:
0.18  360 = 64.8 or about 65
four:
0.10  360 = 36
five or more: 0.04  360 = 14.4 or about 14
Step 4
Use a compass and a protractor to
draw a circle and the appropriate
sections. Label each section and
give the graph a title. Write the
ratios as percents.
Number of Pets
4% five
or more
10%
four
14%
none
18%
three
22%
one
32%
two
Real-World Example 3 Analyze Circle Graphs
JUICE The circle graph at the right shows the
results of a survey about favorite kinds of fruit
juice. If 300 teens were surveyed, how many
more prefer orange juice than grape juice?
Orange
52% of 300 = 0.52  300 or 156
Grape
20% of 300 = 0.20  300 or 60
So, 156 – 60 or 96 more teens surveyed prefer
orange juice than grape juice.
Favorite Fruit Juice
5%
other
8%
pineapple
15%
apple
52%
orange
20%
grape