1. warm-up Handout Correcting pen out Monday & Tuesday – wk 2
Correcting quizzes from Friday

2. Learn to find percent increase and decrease.

3. Percent change is the ratio of the amount of change to the original amount.
Percent increase describes how much the original amount increases.
Percent decrease describes how much the original amount decreases.

4. amount of decrease original amount 4 16
Find the percent increase or decrease from 16 to 12.
This is percent decrease.
16 – 12 = 4
Think: What percent is 4 of 16?
amount of decrease
original amount 4 16

5. 4 16
= 0.25
= 25%
From 16 to 12 is a 25% decrease.

6. This is percent increase.
Find the percent increase or decrease from 15 to 20.
This is percent increase.
20 – 15 = 5
Think: What percent is 5 of 20?
amount of increase
original amount 5 20

7. 5 20
= 0.25
= 25%
From 15 to 20 is a 25% increase.

8. B. In 1999, a certain stock was worth $1. 25 a share
B. In 1999, a certain stock was worth $1.25 a share. In 2002, the same stock was worth $0.85 a share. What was the percent decrease?
1.25 – 0.85 = 0.40
Think: What percent is 0.40 of 1.25?
amount of decrease
original amount
1.25
0.40

9. 1.25
0.40
= 0.32
= 32%
The value of the stock decreased by 32%.

10. A. Sarah bought a DVD player originally priced at $450 that was on sale for 20% off. What was the sale price?
$450  20%
$450  0.20 = $90
The amount of decrease is $90.
Think: The reduced price is $90 less than $450.
$450 – $90 = $360
The sale price of the DVD player was $360.

11. B. Mr. Olsen has a computer business in which he sells everything at 40% above the wholesale price. If he purchased a printer for $85 wholesale, what will be the retail price?
$85  40%
$85  0.40 = $34
The amount of increase is $34.
Think: The retail price is $34 more than $85.
$85 + $34 = $119
The retail price of this printer will be $119.

12. Lesson Quiz
Find each percent increase or decrease to the nearest percent.
1. from 12 to 15
2. from 1625 to 1400
3. from 37 to 125
4. from 1.25 to 0.85
5. A computer game originally sold for $40 but is now on sale for 30% off. What is the sale price of the computer game?
25% increase
14% decrease
238% increase
32% decrease
$28