Applications with Percents

Applications with PercentsObjective:7.1.01 Develop and use ratios, proportions, and

percent to solve problems

Essential Question: How can I apply my understanding

of percents to make more informed shopping decisions?

What is the best “DEAL” or Value?

Vocabulary:Sales Tax: an additional amount of money charged on the

items people buy; the government uses this money to operate the country.

(Not all countries, states or cities have a tax)!Some items are taxed at different rates.

Discount: the amount of money (or percent) by which the regular price of an item is reduced.

Tip: also known as gratuity, is money given to a person who provides a service, and is added to the cost of that service. (In some places it is automatically added!)

Applications with Percents

Real World Choices:Sam has a dilemma. He wants to purchase a game

but cannot decide where to buy it.

Target is selling them for $399.99 with a 15% discount.

Best Buy is selling them for $375.99 but only a 10% discount.

Where should Sam buy his game?

Applications with Percents

But What About If…

Applications with Percents

Real World Example:Target was selling them for $399.99 with a 20%

discount.

Best Buy was selling them for $375.99 and a 15% discount.

Applications with Percents

COMPARE PURCHASE DECISIONS

Store-1 Store-2

Original Cost $399.99 $375.99

Discount Rate 15% 10%

Amount of DiscountHint: Round

.15 x 399.99

.15 x 400 =.1 x 375.99.1 x 376 =

$ Discount $60 $ 37.60

New Price =Original - Discount

400 – 60 = $360

376 – 37.60= $338.4

Applications with PercentsExample 1: Finding Total Cost

A calculator costs $90 and the sales tax is 6%. What is the total cost?

$95.40

Total Cost = Original Cost + Sales TaxFirst calculate the Sales Tax6% OF $90

= 0.06 x 90

$5.40

Total Cost $90.00 + $5.40Total Cost $95.40

Applications with PercentsExample 2: Finding Total Cost

A laptop costs $475 and the sales tax is 7½%. What is the total cost?

$510.63

Total Cost = Original Cost + Sales TaxFirst calculate the Sales Tax

7½% OF $4750.075 x 475

$35.63

Total Cost $475.00 + $35.63Total Cost $510.63

Another way to think about: TOTAL COSTTotal Cost = $Original + $TAX

6% Tax on an Original price of $90. .06 x 90 = $5.40 taxSO: 90 + 5.40 = $95.40

OR:

Total Cost = 90 (1.06)

Total Cost = ORIGINAL x (1 + Rate)

$95.40

Applications with PercentsExample 3: Finding Sale Price

A snowboard has a regular price of $169 but is on sale for 35% off. What is the sale price?

$109.85

Sale Price = Original Cost – DiscountFirst calculate the discount

= 35% OF $169

0.35 x 169$59.15

Total Cost $169.00 – $59.15Total Cost $109.85

Applications with PercentsExample 4: Finding Sale Price

A new coat has a regular price of $185 but is on sale for 33% off. What is the sale price?

$123.95

Sale Price = Original Cost – DiscountFirst calculate the Discount

33% OF $185 0.33 x 185

$61.05

Total Cost $185.00 – $61.05Total Cost $123.95

Another way to think about Sale PriceSales Price = Original - Discount

20% Discount off an Original price of $180. .2 x 180 = $36SO: 180 – 36 = $144

IF the DISCOUNT was 20% , (Percent means 100) SO, that means the Sales Price is

80% of the Original!.8 x 180 = $144.00

Applications with PercentsExample 5: Finding Total Cost

A meal at Pizza Inn cost $25.85. The tax is 8% and Mr. Williams wanted to leave a 15% tip.

What was the TOTAL AMOUNT of the meal?

$31.80

Total Cost = Cost of Meal + Tax + TipFirst calculate

the tax8% OF $25.850.08 x 25.85

$2.07

Next calculate the tip

15% OF $25.850.15 x 25.85

$3.88

25.85$2.07$3.88

Applications with PercentsExample 6: Finding Percent of Discount

An electric guitar was originally $299.95 but on sale for $179.99. What is the percent of discount?

40%

Discount = Original Cost – Sale Price= $299.95 – 179.99= $119.96

Use the Percent Proportion To

Calculate Percent of Discount

ISOF

%100

= =

Applications with PercentsExample 7: Finding Percent of MarkupIn the last 6 months the average price for a gallon of

unleaded gasoline has risen from $2.85 to $3.10. What is the percent of markup?

8.7%

Markup = New Price – Old Price= $3.10 – $2.85= $0.25

Use the Percent Proportion To

Calculate Percent of Discount

ISOF

%100

.0877 = 8.7%

When Calculating Percents of Markup and Discount:

Applications with Percents

Always Remember…You can use the percent proportion or the percent of change formula to make your calculations.

If you choose to use the percent proportion you have to calculate the change first and use that as your IS and use the original price as your OF.

PRACTICE with TAX and DISCOUNTItem Original

CostTax or Discount Rate

Amount of Tax or Discount

Total Cost

CD Player $99.00 5% tax

Computer $1,500.00 25% Discount

Skateboard 119.50 20% Off

Notebook $4.30 8% Tax

Book $24.95 4.5% Tax

Sweater $39.60 40% Discount

Independent Practice:Determine the final cost for each example:

1. $99 CD Player, 5% Tax2. $1,500 Computer, 25% Discount3. $119.50 Skateboard, 20% Off4. $4.30 Notebook, 8% Tax5. $24.95 Book, 4.5% Tax6. $39.60 Sweater, 40% Discount

Applications with Percents

= $103.95= $1125.00

= $$95.60= $4.64

= $26.07= $23.76

Summary:Applications with Percents

Always Remember…

1) Discounts or Sales are subtracted from the original cost of an item

2) Tax is added to the cost of an item

3) To determine the Percent of a Discount or Percent of Markup use the percent proportion or percent change formulas

Applications with PercentsHOMEWORK