A circle is the same as 360°. You can divide a circle into
smaller portions. A part of a circle is called an arc and an arc is
named according to its angle.
A circle graph, or a pie chart, is used to visualize information
and data. A circle graph is usually used to easily show the results
of an investigation in a proportional manner. The arcs of a circle
graph are proportional to how many percent of population gave a
certain answer.
Example:
An investigation was made in Mathplanet high school to
investigate what color of jeans was the most common among the
students. This circle graph shows how many percent of the school
had a certain color. We now want to know how many angles each
percentage corresponds to.
To find out the number of degrees for each arc or section in the
graph we multiply the percentage by 360°.
When we want to draw a circle graph by ourselves we need to
rewrite the percentages for each category into degrees of a circle
and then use a protractor to make the graph.
Example:
If we ask 100 persons which TV program they like the most, we
get this result.
TV program

Persons

Grey's anatomy (GA)

17

Family guy (FG)

34

True blood (TB)

15

Gossip girl (GG)

26

America's funniest home videos (AFV)

8

We know that the total amount of persons is 100. Now we need to
find the ratio for each TV program.
To find the degrees of each TV program we multiply by 360.
And then we use a protractor to draw the chart. It will look
something like this:
Video lesson: Find the values in degrees