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05 – 04C PERCENTS
PERCENT OF
DECREASE OR INCREASE
Old
New
New – Old
Old
Negative answer => Decrease
Positive answer => Increase
PERCENT OF
DECREASE OR INCREASE
August hosted two dinner parties for his friends. Twenty guests
attended the first party, and twenty-nine guests attended the second
party. What is the percentage increase of the number of guests from the
first party to the second party?
New – Old
Old
Negative answer => Decrease
Positive answer => Increase
SALES TAX
An item is priced at $13.24. If the sales tax is 4%, what does the item cost
including sales tax?
Multiply price by sales tax (decimal)
(round to nearest penny)
Now, add the tax to the full price.
$13.24 × 0.04 = $0.53
$13.24 + $0.53 = $13.77
BILL PLUS TIP
Dave rented a limousine for his wife's birthday. The hourly rate is $80. They
used the limousine for 4 hours, plus Dave gave the driver a 20% tip. How
much did he spend in total for the hourly charges plus tip?
First, find the total for the hourly charges.
hourly rate × hours used = $80 × 4 = $320
Next, determine the tip on that total.
20% of $320 = 0.2 × $320 = $64
Finally, find the total of the hourly charges plus the tip.
$320 + $64 =
$384
INTEREST
Tonya took out a loan to help pay for her house. She borrowed $30,000 for 15
years at a yearly simple interest rate of 5%. How much interest will she end up
paying the bank?
The formula for computing simple interest is shown below,
where p is the principal (starting) amount,
r is the interest rate (in decimal form),
and t is the time (in years).
I = prt
The principal is $30,000, the time is 15 years, and the interest rate is 5%, or 0.05.
I
=
=
($30,000)(0.05)(15 yr)
$22,500
INTEREST
Tonya took out a loan to help pay for her house. She borrowed $30,000 for 15
years at a yearly simple interest rate of 5%. How much interest will she end up
paying the bank?
The formula for computing simple interest is shown below,
where p is the principal (starting) amount,
r is the interest rate (in decimal form),
and t is the time (in years).
I = prt
The principal is $30,000, the time is 15 years, and the interest rate is 5%, or 0.05.
I
=
=
($30,000)(0.05)(15 yr)
$22,500
INTEREST
Tonya took out a loan to help pay for her house. She borrowed $30,000 for 15
years at a yearly simple interest rate of 5%. How much interest will she end up
paying the bank?
The formula for computing simple interest is shown below,
where p is the principal (starting) amount,
r is the interest rate (in decimal form),
and t is the time (in years).
I = prt
The principal is $7,000, the rate is 3%, or 0.03, and the interest is $1,050.
INTEREST
Tonya took out a loan to help pay for her house. She borrowed $30,000 for 15
years at a yearly simple interest rate of 5%. How much interest will she end up
paying the bank?
The formula for computing simple interest is shown below,
where p is the principal (starting) amount,
r is the interest rate (in decimal form),
and t is the time (in years).
I = prt
The principal is $7,000, the rate is 3%, or 0.03, and the interest is $1,050.
INTEREST
Bert is planning to open a savings account that earns 1.6%
simple interest yearly. He wants to earn exactly $288 in
interest after 3 years. How much money should he deposit?
The formula for computing simple interest is shown below,
where p is the principal (starting) amount,
r is the interest rate (in decimal form),
and t is the time (in years).
I = prt
The desired interest is $288, the time is 3 years, and the interest
rate is 1.6%, or 0.016.
FIND A PERCENT
Holly missed 6 of 180 school days this year. Approximately what percent of
school days was Holly in attendance?
First, determine how many school days Holly attended.
180 - 6 = 174
Next, find the percentage of school days she attended.
174 ÷ 180 = 0.9666666667
= 97%
DAMAGED ITEMS
Kathleen had a bag of candy-coated chocolates. Of the 60 candies in the bag,
20% were red, 30% were orange, 30% were green, and 20% were blue. Of the
blue ones, 10% had a damaged candy coating. Approximately how many of
the blue ones had a damaged candy coating?
First, determine how many of the candies were blue.
20% of 60 = 0.2 × 60 = 12
Next, find how many of the blue ones were damaged.
10% of 12 = 0.1 × 12 = 1.2
Approximately 1 of the blue ones had a damaged candy coating.
Next, determine the total after the 10% discount.
COUPONS
Nathan took his car in for service and repairs. He had a coupon for 10% off.
Original Prices
Labor $288.37
Parts
$397.03
Other $67.18
Which amount is closest to Nathan's total costs after the 10% discount and
including 7% sales tax? [Assume tax is applied after the discount is applied.]
First, find the total cost for service and repairs.
$288.37 + $397.03 + $67.18 = $752.58
$752.58 - 0.1($752.58) =$752.58 - $75.26
=$677.32
COUPONS CONT.
Finally, apply the 7% sales tax.
$677.32 + 0.07($677.32)
= $677.32 + $47.41
= $724.73
PERCENTS
The value of a professional basketball player's autograph rose 30% in the last
year. It is now worth $364.00. What was it worth a year ago?
(1 + 30%). Convert 30% to 0.3.
$364.00 ÷ (1 + 0.3) = $280.00
% OF DISCOUNT
Jessica purchased a sapphire bracelet during the Jewelry Emporium's SemiAnnual Clearance Sale. If Jessica paid $182.00 for the bracelet and the original
price is $260.00, how much of a discount did she receive?
Original Price - Discount = Sale Price
$260.00 - ($260.00 × p) = $182.00
-$260.00p
$260.00p
p
p
p
=
=
=
=
=
-$78.00
$78.00
$78.00 ÷ $260.00
0.3
30%
DEPOSIT, HOW MUCH IS STILL OWED
Molly is having her birthday party at Pizza Party Palace. The costs involved are
listed below. Pizza Party Palace requires a 20% deposit prior to the date of the
event. If the deposit has been paid, how much is still owed for Molly's party?
•
•
•
Food & Drink
Game Tokens
Other
$200
$100
$60
First, find the total of all party costs.
$200 + $100 + $60 = $360
Next, find 20% of $360.
20% of $360 = 0.2 × $360 = $72
$360 - $72 = $288
MEALS AND GRATITUITY
Brad had a small gathering at a local steakhouse. The steakhouse offers three dinner
platters which vary by size and price. They ordered 4 of the 6-ounce platters, 2 of the 8ounce platters, and 2 of the 11-ounce platters.
Steak Platter Prices
If a gratuity of 18% was added to the bill, which of the following is closest to the total of the
steak platters and gratuity, ignoring sales tax?
•
•
•
6-ounce
8-ounce
11-ounce
$9.95
$12.95
$15.95
First, find the total cost for all dinner platters.
$39.80 + $25.90 + $31.90 =
4($9.95) + 2($12.95) + 2($15.95)
=
$97.60
$17.57
MEALS AND GRATITUITY
Brad had a small gathering at a local steakhouse. The steakhouse offers three dinner
platters which vary by size and price. They ordered 4 of the 6-ounce platters, 2 of the 8ounce platters, and 2 of the 11-ounce platters.
Steak Platter Prices
If a gratuity of 18% was added to the bill, which of the following is closest to the total of the
steak platters and gratuity, ignoring sales tax?
Next, determine the 18% gratuity.
18% of $97.60 = 0.18 × $97.60
$17.57
Finally, find the sum of the dinner platters plus the gratuity.
$97.60 + $17.57 = $115.17
% OF TIME
In his free time, Gary spends 12 hours per week on the Internet and 7 hours
per week playing video games. If Gary has five hours of free time per day,
approximately what percent of his free time is spent on the Internet and
playing video games?
First, find the total time Gary spends on the Internet and playing video games per week.
12 + 7 = 19
Next, determine how much total free time he has each week.
5 × 7 = 35
Finally, determine what percent of his free time is spent on the Internet or playing video games.
19 ÷ 35 = 0.5428571429
Gary spends approximately 54% of his free time on the Internet and playing video games.
PERCENTS
Brian has reduced his cholesterol level by 14% by following a strict diet and
regular exercise. If his original level was 300, what is his cholesterol level now?
COMMISSION
Sandy works at a clothing store. She makes $9 per hour plus earns 15%
commission on her sales. She worked 70 hours over the last two weeks and
had a total of $1,822 in sales before taxes.
Which of the following is closest to how much she will earn in hourly wages
and commission for those two weeks?
First, determine Sandy's earnings based on her hourly wage.
hours worked × hourly wage = 70 × $9 = $630
Next, determine her commission on her total sales.
15% of her total sales = 0.15 × $1,822 = $273.30
Finally, find the sum of her hourly wages plus commission.
$630 + $273.30 = $903.30
THE END