Circle Graphs and Percents

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Circle Graphs and Percents
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Circle Graphs and Percents
Youll have seen circle graphs before in earlier
grades.
Theyre often used to compare different percents.

Circle graphs are useful because they show
clearly how the size of one group relates to
another.
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Circle Graphs and Percents
100 is Equal to the Whole Amount
100 of something is all of it.
Its important to remember this when youre
looking at questions about percents.
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Circle Graphs and Percents
Example 1
Yesenia has a number of marbles. 65 of the
marbles are red. The rest are all blue. What
percent of Yesenias marbles are blue?
Solution
All the marbles are either red or blue.
percent of red marbles percent of blue marbles
all marbles
65 percent of blue marbles 100
percent of blue marbles 100 65
35
So 35 of Yesenias marbles are blue.
Solution follows
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Circle Graphs and Percents
Circle Graphs Are Often Divided into Percents
Circle graphs show how a total splits into
different parts.
The whole circle represents the whole class.
The two sections represent the boys and the girls.
The girls section is larger.
This means the class has more girls than boys.
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Circle Graphs and Percents
When a circle graph shows percents, the whole
circle represents 100.
A section that represents a certain percent fills
that percent of the circle.
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Circle Graphs and Percents
Example 2
This circle graph shows the results of a survey
to find which out of apples, bananas, and
oranges students liked best.
What percent of the students like bananas best?
Solution
The whole circle represents 100, so the total
value of all the sections must be 100.
Call the percent of students who like bananas
best b.
Then 25 35 b 100
The total of all sections is 100
60 b 100
25 35 60
b 100 60 40
Subtract 60 from both sides
So 40 of the students like bananas best.
Solution follows
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Circle Graphs and Percents
Guided Practice
In Exercises 710, find the missing value in each
circle graph.
7.
8.
100 50 50
100 (55 30) 15
9.
10.
100 (31 24) 45
100 (34 19 21) 26
Solution follows
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Circle Graphs and Percents
Guided Practice
A survey asked people which of three drinks they
prefer. This graph shows the number of people
who said they prefer each drink.
11. How many people answered the survey?
20 20 10 50 people
12. What fraction of these people preferred each
drink?
13. What percent of these people preferred each
drink?
Water (1 5) 100 20, Juice (2 5) 100
40, Milk (2 5) 100 40
Solution follows
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Circle Graphs and Percents
Guided Practice
This graph shows the number of insects a
scientist counted for a study.
14. How many insects were there in total?
125 75 125 175 500 insects
15. What percent of each type of insect were
there?
Crickets (125 500) 100 25, Wasps (75
500) 100 15, Bees (125 500) 100 25,
Butterflies (175 500) 100 35
Solution follows
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Circle Graphs and Percents
You Can Turn Percents on Circle Graphs into
Numbers
If you know how many units make up the full 100
of a circle graph, then you can work out how many
each section represents.
then 100 200 people
so 25 50 people
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Circle Graphs and Percents
Example 3
Chris, Martina, and DAndre each ran for student
body president. A total of 150 students voted
in the election, and the outcome of the election
is shown in the circle graph. How many
students voted for Martina?
Solution
The circle graph tells you 40 of the students
voted for Martina. You know that the whole
circle graph represents 150 students.
So the number of students who voted for Martina is
40 of 150 0.4 150 60
A total of 60 students voted for Martina.
Solution follows
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Circle Graphs and Percents
Round Up
Circle graphs are useful for giving out
information.
People who dont know much about math can still
understand what it means when one part of the
circle is bigger than another.
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Circle graphs
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Circle graphs
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Use a circle graph to organize data