1. December 10, 2013
Today:
 Alt.Khan due by End of Period
 Percent Mark-Up/Discount
 Finding Percent Increase/Decrease
 There will be Khan Topics due for all by Dec. 20
 Class Work:
 Prep for Test Tomorrow & Percent Change

2. Vocabulary & Formulas:
Finding Percent Increase & Decrease
 A percent change is an increase or
decrease given as a percent of the original
amount.
 find the % change: from $2.00 to $5.00

3. Vocabulary & Formulas
Section of Notebook
Write the following 4 formulas in this section.
A.
B.
C.
D.
When a number is increased by a certain percent.
When a number is decreased by a certain percent.
Finding original price before a markup.
Finding original price after discount.

4. Example 1: Percent Increase of a Number
A. Find the result when 12 is increased by 50%.
0.50(12) = 6 Find 50% of 12. This is the amount of increase.
12 + 6 =18
It is a percent increase, so add 6 to the
original amount.
12 increased by 50% is 18.
Original Price or number:
Now, the better way…..
X (times) 1 + Decimal form of the
percent
12
X 1.5
18

5. Example 2: Percent Decrease of a Number
B. Find the result when 55 is decreased by 60%.
0.60(55) = 33
Find 60% of 55. This is the amount of decrease.
55 – 33 = 22
It is a percent decrease so subtract 33 from
the original amount.
55 decreased by 60%
is 22. the better way…..In one step, how??
Now,
Original Price or number:
X (times) the compliment of the
Decimal form of the percent
X
55
.4
22

6. Finding Original Price Before Increase
This formula is used to find the original price of an item when
the price is known after increases such as taxes, tips, and
markups.
Original Price:
Price after increase
1 + percent of
The cost of lunch after a 15% tip was $24.15. What was the
cost of the lunch alone?
$24.15
1.15 1 +15% = $21.00

7. Finding Original Price Before Discount
This formula is used to find the original price of an item when
the price is known after the price is discounted.
Original Price:
=
discounted price
Compliment of discount percent
The selling price of an item discounted 20% is $19.20.
What was the original price?
$19.20
.8
Price before discount was $24.00

8. Class Notes & Practice Problems:

9. Example 2: Percent Increase and Decrease
A. Find the result when 72 is increased by 25%.
1.25(72) = 90 72 increased by 25% is
90.
B. Find the result when 10 is decreased by 40%.
0.60(10) = 6 10 times the compliment of the
decrease.
10 decreased by 40%
is 6.

10. Applying Percent Changes
The entrance fee at an amusement park is $35.
People over the age of 65 receive a 20% discount.
What is the amount of the discount? How much do
people over 65 pay?
Method 1: A discount is a percent decrease. So find
$35 decreased by 20%.20% of 35. This is the
Find
0.20(35) = 7
35 – 7 = 28
35 x .8 = 28
amount of the discount.
Subtract 7 from 35. This is the
entrance fee for people over
the age of 65.
Or,… simply multiply $35 by the
compliment of the % discount.

11. Applying Percent Changes
A $220 bicycle was on sale for 60% off. Find the sale
price.
The compliment of 60% is: 100% – 60% =
40%
0.40(220) = 88
Multiply by the compliment
The sale price is $88.
A $220 bicycle went up in price by 25%. Find the new
price.
1.25(220) = $275

12. Practice 1: Percent Markups
The wholesale cost of a DVD is $7. The markup is
85%. What is the amount of the markup? What is the
selling price?
Method 1
The selling price is 185% of the
wholesale price, 7.
100% + 85% = 185%
A markup is a percent increase. So find $7 increased by 85%.
1.85(7) 5.95
0.85(7) = = 12.95
7 + 5.95
12.95 - = 12.95
7 = 5.95
Find 85% of 7. This is the amount of the
Find 185% markup.
of 7. This is the selling price.
Add 12.95. This is the
Subtract fromto 7. This is the selling price.
amount of the markup.
The amount of the markup is $5.95. The selling
price is $12.95.

13. Practice 2: Percent Markups
A video game has a 70% markup. The wholesale cost
is $9. What is the selling price?
A markup is a percent increase. So find $9 increased by 70%.
1.70(9) = 15.30 Find 170% of 9. This is the selling price
This is the amount of the markup
15.30 – 9 =
$6.30
The amount of the markup is $6.30. The selling price is
$15.30.

14. Finding Original Price before Markup
A pair of pants retails for $12.00. This is 50% above
the wholesale cost. What is the wholesale cost?
Original Price:
$12.00
.5
= $8.00
Price after increase
1 + percent of

15. Finding Original Price before Discount
Blah blah blah discounted 30%. Blah blah now
$42.00. Blah Blah blah, find original price.
discounted price
Compliment of discount percent
$42.00
.7
= $60.00

16. Class Work: