Pie Charts - Finding The Percent Of A Number

🔑 Key Concepts

• A pie chart shows how a whole is divided into categories using percentages.
• Each section of a pie chart represents a part of the total.
• To find how many items are in a category, multiply the total by the percent written as a decimal.
• The percentages in a pie chart should add up to \( 100\% \).
• Pie charts help us interpret and compare data visually.

✏️ Worked Examples

Example 1: How Many Students Chose Basketball?

Use this pie chart to answer the following three questions.

The pie chart shows the favorite sports of 40 students. How many students chose basketball as their favorite sport?

From the pie chart, basketball is \( 50\% \) of the class.

Write \( 50\% \) as a decimal.

\( 50\% = 0.50 \)

Multiply the total number of students by the decimal.

\( 40 \times 0.50 = 20 \)

So, 20 students chose basketball.

Example 2: How Many Students Chose Soccer?

The same pie chart represents 40 students. How many students chose soccer as their favorite sport?

From the pie chart, soccer makes up \( 25\% \) of the class. This means that out of every 100 students, 25 would choose soccer.

Since our class only has 40 students, we find 25% of 40.

First, write the percent as a decimal.

\( 25\% = 0.25 \)

Then multiply the total by the decimal.

\( 40 \times 0.25 = 10 \)

This calculation tells us how many students fall into the soccer category.

So, 10 students chose soccer.

Example 3: How Many Students Chose Football or Other?

The pie chart represents 40 students. How many students chose football or other as their favorite sport?

Football represents \( 20\% \) and Other represents \( 5\% \) of the class.

Because the question asks about both categories together, we add the percentages first.

\( 20\% + 5\% = 25\% \)

Now convert the percent to a decimal.

\( 25\% = 0.25 \)

Multiply by the total number of students.

\( 40 \times 0.25 = 10 \)

This result represents the combined number of students who selected either football or other.

So, 10 students chose football or other.

🧠 Math Vocabulary

• Pie Chart: a circular graph that shows how a whole is divided into parts.
• Percent: a ratio out of \( 100 \).
• Total: the entire number of items or people being represented.
• Category: one group or section in a data display.
• Data: information collected and organized for interpretation.

💡 Main Idea

Pie charts help us understand how a total is divided into categories. By reading the percentages in each section and using the total number of items, we can determine how many belong to each category. This connects visual data displays to percent calculations and real-world interpretation.

📚 What You Should Already Know

Before working with pie charts, students should know how to convert a percent to a decimal and how to find a percent of a number by multiplying. It also helps to understand that percentages describe parts of a whole out of \( 100 \).

🚀 What Comes Next

After interpreting pie charts, students can move on to creating their own data displays, comparing data across categories, and solving more advanced percent applications involving surveys, statistics, and real-world data analysis.

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