What Are Pie Charts?

What are Pie Charts?

Concept

A pie chart is a pictorial representation of data in the form of a circular chart or pie where the slices of the pie show the size of the data. A list of numerical variables along with categorical variables is needed to represent data in the form of a pie chart. The arc length of each slice and consequently the area and central angle it forms in a pie chart is proportional to the quantity it represents. It is one of the most commonly used graphs to represent data using the attributes of circles, spheres, and angular data to represent real-world information. The shape of a pie chart is circular where the pie represents the whole data and the slice out of the pie represents the parts of the data and records it discretely.

Rules

We know that the total value of the pie is always 100%. It is also known that a circle subtends an angle of 360°. Hence, the total of all the data is equal to 360°. Based on these, there are two main formulas used in pie charts:
Calculate the percentage of the given data:

$\fn_phv Percent\;of\;given\;data =\frac{Frequency\;of\;data}{Total\;Frequency}\times 100%$

Find angle of pie chart section:
The arc length is a fraction of the circumference. The sector area is a fraction of the whole area. The sector angle is a fraction of 360°

$\fn_phv Angle\;of\;sector=\frac{Frequency\;of\;data}{Total\;Frequency}\times 360^{\circ}$

Example

The pie chart displays the favorite dog breed of 50 students. How many students chose poodles?

Solution

18 % of 50 students chose poodles.
Number of students = $\fn_phv \frac{18}{100}$ × 50 = 9
Answer: 9 students

Practice What are Pie Charts

Practice Problem 1

The pie chart represents the number of children who participate in a variety of sports. What sport has the least children’s participation?

Practice Problem 2

The pie chart represents the percentage of votes students received during a school election. What percentage of the students did NOT vote for the winning student?

Practice Problem 3

The pie graph displays the type of fast food that 50 students preferred to eat for lunch. How many students preferred hamburgers?

Practice Problem 4

In a pie chart representing the percentages of students who enjoy reading various kinds of books, the central angle of the slice representing students who enjoy reading science fiction is 72°. What is the percentage of students interested in reading science fiction?