1. 8.4 Percent of Increase and Decrease

2. Percent increase describes how much the original amount increases.
Percent change is the ratio of the amount of change to the original amount.
The Difference
Original Amount
Percent Change =
x 100
Percent increase describes how much the original amount increases.
Percent decrease describes how much the original amount decreases.

3. Remember a ratio can be written as a fraction!
Percent of Change
Remember a ratio can be written as a fraction!
amount of change x 100 = % of
original amount change

4. golf course on Monday. On Friday he shot a 95. What is the % of
Problem # 1
Zack Cole shot an 86 on the
golf course on Monday. On Friday
he shot a 95. What is the % of
change?
Is the score increasing or decreasing?

5. Because score was going up!
Answer #1
amount of change x 100
original amount
= 9 = (100) =
10.5% Increase
Because score was going up!

6. Kelly Dyer became a great writer. She had a picnic each
Problem # 2
Kelly Dyer became a great
writer. She had a picnic each
year to celebrate the date of her
first published work. The 1st
year 50 people came. The 2nd
year 30 people came. What is
the percent of change?

7. Because the amount of people decreased from year 1 to year 2!
Answer #2
50-30 = 20 = 0.4(100)
50 50
40% Decrease
Because the amount of people decreased from year 1 to year 2!

8. Last six weeks Joseph Lawhorn made an 88 average in class.
Problem # 3
Last six weeks Joseph Lawhorn
made an 88 average in class.
This six weeks he made a 92.
Please figure the percent
of change.

9. Because his average is going up!
Answer #3
92-88 = 4 = (100)
4.5% Increase
Because his average is going up!

10. famous architect. She made $90,000 in 2004. In 2005 she
Problem # 4
Angela Smyre became a
famous architect. She made
$90,000 in In 2005 she
made $120,000. What is the
percent of increase?

11. Answer #4
120, ,000 = 30,000= .33(100)
90, ,000
33.3% Increase

12. Amber Robinson became a foster mother, because she is so good with
Problem # 5
Amber Robinson became a foster
mother, because she is so good with
children. She took care of 8
children in In 2004 she had
only 5. What is the percent of
change?

13. Answer #5
8 - 5 = 3 = (100)
37.5% Decrease

14. period. What is the percent
Problem # 6
Jonathan Rogers drew 47 planes in
4th period. He drew 28 in 5th
period. What is the percent
of change?

15. Answer #6
40.4% Decrease

16. last year. He bought only 35 this year. (He lost all his
Problem # 7
Matt Viers bought 42 CD’s
last year. He bought only
35 this year. (He lost all his
money in the stock market) What
is the percent of change?

17. Answer #7
16.7% Decrease

18. great singer. She was so famous she had 12 body guards at one
Problem # 8
Lisa LaViers became a
great singer. She was so famous
she had 12 body guards at one
concert. At the next concert she
had 15 body guards. What is
the percent of change?

19. Answer #8
25% Increase

20. Jessica Summey and Emily Lower were famous mud wrestlers. They
Problem # 9
Jessica Summey and Emily Lower
were famous mud wrestlers. They
made $45,000 in In
2009 they made $60,000. What is
the percent of change?

21. Answer #9
33.3% Increase

22. Brittany Berrier became a famous doctor. She took out 15 gall
Problem # 10
Brittany Berrier became a famous
doctor. She took out 15 gall
bladders on May 15th. She took out
30 on May 18th. What is the % of
change?

23. Answer #10
100% Increase