1. Percent of Change

2. 1. What is 20% of 70? 2. What percent of 24 is 18? 3. 32 is 10% of what number?

3.  Percent of Change : The percent a quantity increases or decreases compared to the original amount.  Increase: Goes up, gets bigger, gets larger, grows, more  Decrease: Goes down, gets smaller, shrinks, less Amount of change: Start minus finish

4.  Try this on your calculator 18 – 10 = 8 Went down 8 10 – 18 = – 8 Went up 8 You can tell if they went up or down without a calculator, so just ignore the negative & use 8 either way.

5. Ignore negatives or use absolute value! The amount of change is the absolute value of the difference between the new amount and the original amount.

6. Example 1 Find the % of change from $10 to $18 = ? 100 10 18 – 10 Solve: = 80 Going from $10 to $18 is an 80% increase

7. Example 2 Find the percent of decrease from 25 to 21 Example 1 = ? 100 25 25 – 21 Solve: = 16 Going from 25 to 21 is a 16% decrease

8. Identify the percent of change as an increase or a decrease. Find the percent of change. Round percents to the nearest tenth if necessary. 1. 4 to 5 2. 20 to 16 3. 12 to 6

9. Find the percent of decrease from 25 to 21.  Calculate the amount of decrease. 25 – 21 = 4  Calculate the percent of decrease.  The percent of decrease from 25 to 21 is 16%.

10. Last year 2300 people attended a Fourth of July parade at the beach. This year the number of people increased by 8%. Find the number of people who attended the parade this year.  Use the percent of change equation.  Write the percent as a decimal.  Multiply both sides by 2300. 184 = x  There were 184 more people this year.  Add to last year’s number for total. 2300 + 184 = 2484  There were 2,484 people at the parade this year.

11. Do you think there has been a percent increase or a percent decrease in the total number of students in your school compared to ten years ago? Why?

12. Targets: Find the percent of increase or the percent of decrease between two numbers. Use percent of change to find new values.

14. Find the percent of increase from 10 to 18.  Calculate the amount of increase. 18 – 10 = 8  Calculate the percent of increase.  The percent of increase from 10 to 18 is 80%. Example 1

15. In 1999, Hernandez paid $2,000 for a new laptop computer. In 2007, Hernandez paid 60% less for a laptop computer than he had in 1999. Find the amount he paid in 2007.  Use the percent of change equation.  Write the percent as a decimal.  Multiply both sides by 2,000. 1200 = x  Hernandez paid $1,200 less in 2007 than in 1999.  Subtract 1200 from the value in 1999. 2000 – 1200 = 800  Hernandez paid $800 for a laptop computer in 2007.