Math on the Mind

Which is the better deal:▫20% off a $240 video game system

▫15% off a $210 video game system

Percent of ChangeUnit 4, Lesson 12Mrs. King

Picture from hoffnermath.wordpress.com

Percents Refresher:

drugstoredivas.net

Vocabulary

•Wholesale Price = the price that stores pay for merchandise

•Retail Price = the price at which stores sell merchandise

•Mark up = an increase in price•Discount = a reduction in price

Formula for percent change:

price original

change ofamount

100

percent

Difference between the

“new” and the “original”

Find each percent of change. Describe the percent of change as an increase or decrease.

1. $6 to $9 2. 15 cm to 12 cm

x = 50% increase

20% decrease

Examples:

price original

change ofamount

100

percent

100

3

6x=300

x6

66

100

3

15x=300

x15

1515

Example #1

•An auto mechanic purchases a set of tires at a price of $250 an sells them for $310. What is the percent markup in price?

price original

change ofamount

100

percent

100x

250310-25060

250x=6000

x=24

Example #2

•A sweater is on sale for 20% off the retail price. If the sweater is priced at $70, what is the sale price?

price original

change ofamount

100

percent

10020 70

x

100x=1400

x=14

70-1456

Example #3

•A toy store buys toys at whole sale and issues a markup of 15%. If the store buys a train set for $50, at what price will the store sell the train?

price original

change ofamount

100

percent

10015 50

x

100x=750

x=7.50

50+ 7.5057.50

The price of a skirt decreased from $32.95 to $28.95. Find

the percent of decrease.

32.95 – 28.9532.95

=

x 12%

4 32.95

=

Example:

price original

change ofamount

100

percent

x100

x100

32.95x = 40032.95 32.95

Between 1940 and 1980, the federal budget increased from

$9.5 billion to $725.3 billion. What was the percent of

increase in the federal budget?

=725.3 – 9.5

9.5

= 715.89.5

= 7535%

Example:

price original

change ofamount

100

percent

x100x

100

9.5x = 715809.5 9.5

The Booster Club allows a maximum 70% markup for fundraising.

If the donuts cost us $.89 apiece, what is the highest price we could charge for the

donuts?

original

changepercent

100

89.0100

70 x

3.62100 x100 100

62.0$623. x

51.1$89.0$62.0$

Let’s sell the donuts for $1.50 each—it’s easier to make change that way!

The day is coming to an end and we still have some donuts left.

We decide to post a sign:

What is the new price?

original

changepercent

100

50.1100

25 x

5.37100 x100 100

38.0$375. x

12.1$38.0$50.1$

What is the percent increase from the original purchase price to the new selling

price?

original

changepercent

100

89.0

89.012.1

100

x

2389.0 x89.0 89.0

%8.25x

89.0

23.0

100

x