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