CHAPTER 8. Consumer Mathematics and Financial Management Pearson Prentice Hall. All rights reserved.

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1 CHAPTER 8 Consumer Mathematics and Financial Management 2010 Pearson Prentice Hall. All rights reserved.

2 8.1 Percent, Sales Tax, and Income Tax 2010 Pearson Prentice Hall. All rights reserved. 2

3 Objectives 1. Express a fraction as a percent. 2. Express a decimal as a percent. 3. Express a percent as a decimal. 4. Solve applied problems involving sales tax and discounts. 5. Compute income tax. 6. Determine percent increase or decrease. 7. Investigate some of the ways percent can be abused Pearson Prentice Hall. All rights reserved. 3

4 Basics of Percent Percents are the result of expressing numbers as a part of 100. The word percent means per hundred. Expressing a fraction as a percent: 1. Divide the numerator by the denominator. 2. Multiply the quotient by 100. This is done by moving the decimal point in the quotient two places to the right. 3. Add a percent sign Pearson Prentice Hall. All rights reserved. 4

5 Example 1: Expressing a Fraction as a Percent 5 Express 8 Solution: as a percent. Step 1. Divide the numerator by the denominator. 5 8 = Step 2. Multiply the quotient by 100. Step 3. Add a percent sign. 5 Thus, = 62.5% = % 2010 Pearson Prentice Hall. All rights reserved. 5

6 Expressing a Decimal as a Percent To express a decimal as a percent: 1. Move the decimal point two places to the right. 2. Attach a percent sign Pearson Prentice Hall. All rights reserved. 6

7 Example 2: Expressing a Decimal as a Percent Express 0.47 as a percent. Solution: Thus, 0.47 = 47% Pearson Prentice Hall. All rights reserved. 7

8 Expressing a Percent as a Decimal Number To express a percent as a decimal number: 1. Move the decimal point two places to the left. 2. Remove the percent sign Pearson Prentice Hall. All rights reserved. 8

9 Example 3: Expressing Percents as Decimals Example: Express each percent as a decimal: a. 19% b. 180% Solution: Use the two steps. a. Thus, 19% = b. 180% = 1.80 or Pearson Prentice Hall. All rights reserved. 9

10 Percent, Sales Tax, & Discounts Many applications involving percent are based on the following formula: Note that of implies multiplication. We use this formula to determine sales tax collected by states, counties, cities on sales items to customers. Sales tax amount = tax rate item s cost 2010 Pearson Prentice Hall. All rights reserved. 10

11 Example 4: Percent and Sales Tax Suppose that the local sales tax rate is 7.5% and you purchase a bicycle for $894. a. How much tax is paid? b. What is the bicycle s total cost? Solution: a. Sales tax amount = tax rate item s cost 7.5% $894 = $894 = $67.05 The tax paid is $ b. Total Cost = $ $67.05 = $ The bicycle s total cost is $ Pearson Prentice Hall. All rights reserved. 11

12 Percent and Sales Price Businesses reduce prices, or discount, to attract customers and to reduce inventory. The discount rate is a percent of the original price. Discount amount = discount rate original price Pearson Prentice Hall. All rights reserved. 12

13 Example 5: Percent and Sales Price A computer with an original price of $1460 is on sale at 15% off. a. What is the discount amount? b. What is the computer s sale price? Solution: a. Discount amount = discount rate original price The discount amount is $ Pearson Prentice Hall. All rights reserved. 13

14 Example 5: Percent and Sales Price continued b. A computer s sale price is the original price, $1460, minus the discount amount, $219. Sale price = $1460 $219 = $1241 The computer s sale price is $ Pearson Prentice Hall. All rights reserved. 14

15 Percent and Income Tax Calculating Income Tax: 1. Determine your adjusted gross income: 2. Determine your taxable income: 2010 Pearson Prentice Hall. All rights reserved. 15

16 Percent and Income Tax 3. Determine the income tax: 2010 Pearson Prentice Hall. All rights reserved. 16

17 Percent and Income Tax The table shows tax rates, standard deductions, and exemptions for the four filing status categories Pearson Prentice Hall. All rights reserved. 17

18 Example 6: Computing Income Tax Example: Calculate the income tax owed by a single woman with no dependents whose gross income, adjustments, deductions, and credits are given. Use the marginal tax rates from the table. Single Woman with no dependents: Gross income: $62,000 Adjustments: $4,000 Tax credit: $500 Deductions: $7500: mortgage interest $2200: property taxes $2400: charitable contributions $1500: medical expenses not covered the insurance 2010 Pearson Prentice Hall. All rights reserved. 18

19 Solution: Percent and Income Tax Example Continued Step 1. Determine the adjusted gross income. Adjusted gross income = Gross income Adjustments = $62,000 $4000 = $58, Pearson Prentice Hall. All rights reserved. 19

20 Example 6 continued Step 2. Determine taxable income. We substitute $12,100 for deductions in the formula for taxable income Pearson Prentice Hall. All rights reserved. 20

21 Example 6 continued Taxable income = Adjusted gross income (Exemptions + Deductions) = $58,000 ($ $12,100) = $58,000 $15,600 = $42,400 Step 3. Determine the income tax. Income tax = Tax computation Tax credits = Tax Computation $500 Since the single woman taxable income is $42,400 she falls in the tax bracket of 25% Pearson Prentice Hall. All rights reserved. 21

22 Example 6 continued This means that she owes: 10% on the first $8025 of her taxable income, 15% on her taxable income between $8026 to $32,500, inclusive, and 25% on her taxable income above $32, Pearson Prentice Hall. All rights reserved. 22

23 Example 6 continued = 0.10 $ ($32,550 $8025) ($42,400 $32,550) = 0.10 $ ($24,525) $9850 = $ $ $ = $ We substitute $ for the tax computation in the formula for income tax. Income tax = Tax computation Tax credits = $ $500 = $ Thus, the income tax owed is $ Pearson Prentice Hall. All rights reserved. 23

24 Percent and Change If a quantity changes, its percent increase or its percent decrease can be found as follows: 1. Find the fraction for the percent increase or decrease: amount of increase original amount or amount of decrease original amount. 2. Find the percent increase or decrease by expressing the fraction in step 1 as a percent Pearson Prentice Hall. All rights reserved. 24

25 Example 7: Finding Percent Increase and Decrease In 2000, world population was approximately 6 billion. The data are from United Nations Family Planning Program and are based on optimistic or pessimistic expectations for successful control of human population growth. a. Find the percent increase in world population from 2000 to 2150 using the high projection data. b. Find the percent decrease in world population from 2000 to 2150 using the low projection data Pearson Prentice Hall. All rights reserved. 25

26 Example 7: Finding Percent Increase and Decrease continued Solution: a. Use the data shown on the blue, high-projection, graph. The projected percent increase in world population is 400% Pearson Prentice Hall. All rights reserved. 26

27 Example 7: Finding Percent Increase and Decrease continued b. Use the data shown on the green, low-projection, graph. Percent decrease amount of decrease original amount % The projected percent decrease in world population is 33⅓% Pearson Prentice Hall. All rights reserved. 27

28 Example 9: Abuses of Percents John Tesh, while he was still co-anchoring Entertainment Tonight, reported that the PBS series The Civil War had an audience of 13% versus the usual 4% PBS audience, an increase of more than 300%. Did Tesh report the percent increase correctly? Solution: We begin by finding the actual percent increase. amount of increase Percent increase original amount % The percent increase for PBS was 225%. This is not more than 300%, so Tesh did not report the percent increase correctly Pearson Prentice Hall. All rights reserved. 28