Chapter 9

Playing the Percentages

In This Chapter

arrow Converting between percents and decimals

arrow Switching between percents and fractions

arrow Solving all three types of percent problems

Like fractions and decimals (which I discuss in Chapters 6, 7, and 8), percents are a way of describing parts of the whole. The word percent literally means “for 100,” but in practice, it means “out of 100.” So, when I say that 50 percent of my shirts are blue, I mean that 50 out of 100 shirts — that is, half of them — are blue. Of course, you don't really have to own as many shirts as I claim to in order to make this statement. If you own 8 shirts and 50 percent of them are blue, then you own 4 blue shirts.

In this chapter, I show you how to convert percents to and from decimals and fractions. In the last section, I show you how to translate percent problems into equations to solve the three main types of percent problems. Become familiar with percents, and you'll be able to figure out discounts, sales tax, tips for servers, and my favorite: interest on money in the bank.

Converting Percents to Decimals

Percents and decimals are very similar forms, so everything you know about decimals (see Chapter 8) carries ...

Get Basic Math and Pre-Algebra Workbook For Dummies, 2nd Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.