Chapter 3
Decimals
Student Performance Objectives:
Section I Understanding Decimal Numbers
3-1 Reading and Writing Decimal Numbers in Numerical and Word Form
Section II Decimal Numbers and the Fundamental Processes
3-3 Adding and Subtracting Decimals
Section III Conversion of Decimals to Fractions and Fractions to Decimals
3-6 Converting Decimals to Fractions
Chapter Notes, Teaching Tips and Lecture Launchers
• Students need to recognize that decimals are used extensively in business applications,
particularly those involving money. Even stock prices are now expressed in decimals.
Proficiency with decimals is essential for a well-trained “business mind.”
most students enjoy doing because it involves one of their favorite subjects, sports.
• Spotlight: The Business Decision, “Administering a Government Program” in the
Section II exercise set, asks students to assume the role of administrator. Here, they must
Section I Understanding Decimal Numbers
• Be sure students keep in mind that decimals are just another way of expressing “parts” of a
whole thing.
• Encourage students to practice rounding decimal numbers to whole numbers, tenths,
hundredths (dollars and cents) and thousandths. This is very important in business.
• For example, the Internal Revenue Service, IRS, requests that numbers on tax returns
• Collaborative Learning Activity: In business, numerical values are often given over the
telephone. Have students break into groups of two’s. Ask them to alternate with their
partner, verbally communicating a decimal number, while the other partner writes the
number down.
• For example, eighteen and three tenths, 18.3; or fifty-four and twenty-three
Section II Decimal Numbers and the Fundamental Processes
• Stress the point that generally, except when “estimating,” decimal numbers should not be
rounded until the final answer. When rounding for estimating, round only the multiplier and
multiplicand, not the product.
• In addition and subtraction, point out the importance of lining up the decimal points. Remind
students the decimal is assumed to be to the right of the last digit of a whole number.
• Emphasize the point that in multiplication of decimals, the product has the same number of
places as are contained in the multiplier and multiplicand.
Section III Conversion of Decimals to Fractions and Fractions to Decimals
• Show students that a decimal written as .66
6
means a repeating decimal, representing the
fraction
2
3
. Have students use their calculators to find others. (
1
3
1
6
5
6
, , 1
9, 4
9
,
,
23
9
)
• Spotlight: When converting decimals to fractions, ask student to verbally “say” the decimal,
• Converting decimal inches to fractional inches.
Questions Students Always Ask
“Can I solve problems involving fractions by converting to decimals?”
“How do I know when to round?”
• When estimating, the components of the equation should be rounded all the way, i.e.
“How do I know what place to round to?”
• Pay careful attention to the question; to what place does it ask you to round? If the
“I’m doing the problem just the way you say, but I’m getting the wrong answer.”
• Check to make sure your calculator isn’t rounding when it shouldn’t be. For this class,
it’s best to set your calculator to floating decimal.
“How do I convert .05 ½ to a pure decimal?”