1. What is Percent of Change?
Common Examples of Percent of Increase
Common Examples of Percent of Decrease
Sales tax on an item purchased
Items that are on sale at a store
Finding a total bill at a restaurant including tip
Population decreases

2. Percent of Change
Percent of Change: the amount, stated as a percent, that a number increases or decreases.
Percent of Increase: The amount, stated as a percent, that a number goes up.
Percent of Decrease: The amount, stated as a percent, that a number goes down.

3. Percent of Change
Percent of Change = amount of change
original amount

4. Finding Percent of Change
27 is decreased to 20
27 – 20 = 7
Percent of Change = amount of change
original amount
Percent of Change = 7 27
Percent of Change ≈
Percent of Change ≈ 25.9%

5. Finding Percent of Change
32 is increased to 67
67 – 32 = 35
Percent of Change = amount of change
original amount
Percent of Change = 35 32
Percent of Change ≈
Percent of Change ≈ 109.4%

6. Finding Percent of Change
20 is decreased to 11
20 – 11 = 9
Percent of Change = amount of change
original amount
Percent of Change = 9 20
Percent of Change ≈ 0.45
Percent of Change ≈ 45%

7. Finding Percent of Change
42 is increased to 72
72 – 42 = 30
Percent of Change = amount of change
original amount
Percent of Change = 30 42
Percent of Change ≈
Percent of Change ≈ 71.4%

8. Finding Percent of Change Your Turn…
24 is increased to 30
Percent of Change = amount of change
original amount

9. Finding Percent of Change Your Turn…
56 is decreased to 14
Percent of Change = amount of change
original amount

10. Finding Percent of Change Your Turn…
105 is decreased to 32
Percent of Change = amount of change
original amount

11. Finding Percent of Change Word Problems
Zack Cole shot an 86 on the golf course on Monday. On Friday he shot a 95. What is the % of change?
86 increased to 95
Percent of Change = amount of change = 9
original amount
Percent of Change = 10.5%

12. Finding Percent of Change Word Problems
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?
50 decreased to 30
Percent of Change = amount of change = 20
original amount
Percent of Change = 40%

13. Finding Percent of Change Word Problems: Your Turn
Last six weeks Joseph Lawhorn made an 88. This six weeks he made a 92. Please figure the percent of change.

14. Finding Percent of Change Word Problems: Your Turn
Angela Smyre became a famous architect. She made $90,000 in In 2005 she made $120,000. What is the percent of increase?

15. Finding Percent of Change Word Problems: Your Turn
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?

16. Using Percent of Change
When you know the percent of change, you can use an equation, or proportion to find the actual amount.

17. Using Percent of Change
The regular price of a portable CD player at Edwin’s Electronics is $ This week it is on sale for 25% off. Find the amount of the discount.
Part (is) = Part %
Original Whole (100%)
x = 25
100x = x = ≈ $8

18. Using Percent of Change
The regular price of a portable CD player at Edwin’s Electronics is $ This week it is on sale for 25% off. Now, Find the sale price.
x = ≈ $8
$ $8.00 = $23.99
The sale price is $23.99

19. Using Percent of Change
The retail price of a pair of shoes is a 98% increase from its wholesale price. If the wholesale price is $12.50, what is the retail price?
Part = Part %
Original Whole (100%)
x = 98
100x = x = $12.25

20. Using Percent of Change
The retail price of a pair of shoes is a 98% increase from its wholesale price. If the wholesale price is $12.50, what is the retail price?
x = $12.25
$ $12.25 = $24.75
The retail price is $24.75

21. Using Percent of Change
The regular price of a sweater is $ It is on sale for 20% off. Find the amount of the discount and sale price.
Part = Part %
Original Whole (100%)
x = 20
100x = x = $8.598 ≈ $8.60

22. Using Percent of Change
The regular price of a sweater is $ It is on sale for 20% off. Find the amount of the discount and sale price.
x = $8.60
$ $8.60 = $34.39
The sale price is $34.39

23. Using Percent of Change Your Turn
A backpack that usually sells for $39 is on sale for 33% off. Find the amount of the discount and the sale price.

24. Using Percent of Change Your Turn
A sporting good store is having a closeout on a certain style of running shoes. They are marked 55% off the regular price. Find the amount of the discount and the sale price.

25. Using Percent of Change Your Turn
A gallery owner purchased a very old painting for $3,000. The painting sells at a 325% increase in price. What is the retail price of the painting?