Trigonometry Workbook For Dummies
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A pie chart, which looks like a divided circle, shows you how a whole object is cut up into parts. Pie charts are most often used to represent percentages. For example, the following figure is a pie chart representing Eileen’s monthly expenses.

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You can tell at a glance that Eileen’s largest expense is rent and that her second largest is her car. Unlike a bar graph, the pie chart shows numbers that are dependent upon each other. For example, if Eileen’s rent increases to 30% of her monthly income, she’ll have to decrease her spending in at least one other area.

Here are a few typical questions you may be asked about a pie chart:

  • Individual percentages: What percentage of her monthly expenses does Eileen spend on food? Find the slice that represents what Eileen spends on food, and notice that she spends 10% of her income there.

  • Differences in percentages: What percentage more does she spend on her car than on entertainment? Eileen spends 20% on her car but only 5% on entertainment, so the difference between these percentages is 15%.

  • How much a percent represents in terms of dollars: If Eileen brings home $2,000 per month, how much does she put away in savings each month? First notice that Eileen puts 15% every month into savings. So you need to figure out 15% of $2,000. Solve this problem by turning 15% into a decimal and multiplying:

    0.15 2,000 = 300

    So Eileen saves $300 every month.

About This Article

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About the book author:

Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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