Overview

The purpose of this lesson is to review circle graphs and displaying information.

Read

A circle graph, sometimes called a pie graph, is a visual way to display data using circles and parts of a circle. In fact, circle graphs are one of the most popular means of displaying real-world data.

In a circle graph, the entire circle represents 100% and each section of the circle represents some part out of 100.

Example

A soil sample below a chemical warehouse was sampled for possible contamination. Below are the results.

Data set 1: Magnesium

Data set 2: Nitrogen

Data set 3: Carbon

Data set 4: Calcium

The circle graph below shows how a graph is divided into sections according to the data. Data Set 1 is 25% of the graph. This is displayed numerically as well as visually. Notice that the green section of the circle is one-fourth, or 25%, of the circle.

Data Set 2 is 50% or one-half of the entire circle. Again, this is represented numerically and by the proportion of the circle it occupies.

Data Set 3, with 10%, and Data Set 4, with 15%, account for a total of one-fourth, or 25%, of the circle.

You can use circle graphs to easily answer questions about data and to compare and contrast sections of data with other sections and against the whole data set.

Example

The circle graph below displays data about students' future occupational goals

[Figure4]

What percent of the students aspire to work in science and research?

To figure this out, look at the whole of the circle and remember that it is equal to 100%. First, note the known percentages:

20% want a career in healthcare.
15% want a career in the legal field.
10% want a career in law enforcement.
5% want a career in the military.
30% want a career in computers.

Then, there is an unknown percent of the students that want to work in science and research. To determine how many want to work in science and research add the known percentages and subtract the total from 100 percent.

$20 + 15 + 10 + 5 + 30 = 80$

$100 - 80 = 20$

The answer is 20% of the students want a career in science and research.

Circle Graphs by CK-12 is licensed under CC BY-NC 3.0