Pre-Algebra 8-4 Percent Increase and Decrease Our Learning Goal Students will be able to determine and construct fractions, decimals, and percents by understanding their relationships, solving for the unknown, solving increase and decrease, solving sales tax/total cost contextual problems and compute simple interest.

Pre-Algebra 8-4 Percent Increase and Decrease Pre-Algebra HOMEWORK Page #17-25 & Spiral Review ANSWERS

Pre-Algebra 8-4 Percent Increase and Decrease Pre-Algebra Homework Page 419 #30-36 & Spiral Review (#37-40)

Our Learning Goal Assignments Learn to relate decimals, fractions, & percents (8-1) Learn to find percents (8-2) Learn to find a number when the percent is known (8-3) Learn to find percent increase and decrease (8-4) Learn to estimate with percents (8-5) Learn to find commission, sales tax, and withholding tax (8-6) Learn to compute simple interest (8-7)

Pre-Algebra 8-4 Percent Increase and Decrease Learning Goal Scale Students are able to determine & construct fractions, decimals, & percents: Clear understanding their relationships Able to solve for the unknown Understands how to solve for increase & decrease Calculating solving sales tax/total cost contextual problems Computing simple interest Understands their relationships Some solving for the unknown Difficulty solving for increase & decrease Understands their relationships Difficulty solving for the unknown Some understanding their relationships Even with help, no understanding or skill demonstrated

Pre-Algebra 8-4 Percent Increase and Decrease Student Learning Goal Chart

Pre-Algebra 8-4 Percent Increase and Decrease 8-4 Percent Increase and Decrease Pre-Algebra Warm Up Warm Up Problem of the Day Problem of the Day Lesson Presentation Lesson Presentation

Pre-Algebra 8-4 Percent Increase and Decrease Warm Up 1. 14,000 is 2 % of what number? is 13% of what number? % of what number is 12? % of what number is 189? 560, Pre-Algebra 8-4 Percent Increase and Decrease

Pre-Algebra 8-4 Percent Increase and Decrease Problem of the Day In a school survey, 45% of the students said orange juice was their favorite juice, 25% preferred apple, and 10% preferred grapefruit. The remaining 32 students preferred grape juice. How many students participated in the survey? 160 students

Pre-Algebra 8-4 Percent Increase and Decrease Today’s Learning Goal Assignment Learn to find percent increase and decrease.

Pre-Algebra 8-4 Percent Increase and Decrease Vocabulary percent change percent increase percent decrease

Pre-Algebra 8-4 Percent Increase and Decrease Percents can be used to describe a change. 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. amount of change original amount percent change =

Pre-Algebra 8-4 Percent Increase and Decrease Find the percent increase or decrease from 16 to 12. Additional Example 1: Percent Increase and Decrease This is percent decrease. 16 – 12 = 4First find the amount of change. Think: What percent is 4 of 16? amount of decrease original amount 4 16 Set up the ratio.

Pre-Algebra 8-4 Percent Increase and Decrease Additional Example 1 Continued = 25%Write as a percent. = 0.25Find the decimal form From 16 to 12 is a 25% decrease.

Pre-Algebra 8-4 Percent Increase and Decrease Find the percent increase or decrease from 15 to 20. Try This: Example 1 This is percent increase. 20 – 15 = 5First find the amount of change. Think: What percent is 5 of 20? amount of increase original amount 5 20 Set up the ratio.

Pre-Algebra 8-4 Percent Increase and Decrease Try This: Example 1 Continued = 25%Write as a percent. = 0.25Find the decimal form From 15 to 20 is a 25% increase.

Pre-Algebra 8-4 Percent Increase and Decrease A. When Jim was exercising, his heart rate went from 70 beats per minute to 98 beats per minute. What was the percent increase? Additional Example 2: Life Science Application Think: What percent is 28 of 70? Set up the ratio. 98 – 70 = 28First find the amount of change. amount of increase original amount

Pre-Algebra 8-4 Percent Increase and Decrease Additional Example 2 Continued = 40%Write as a percent. = 0.4Find the decimal form Jim’s heart rate increased by 40% when he exercised.

Pre-Algebra 8-4 Percent Increase and Decrease 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? Additional Example 2B: Application 1.25 – 0.85 = 0.40First find the amount of change. Think: What percent is 0.40 of 1.25? amount of decrease original amount Set up the ratio.

Pre-Algebra 8-4 Percent Increase and Decrease Additional Example 2B Continued = 32%Write as a percent. = 0.32Find the decimal form The value of the stock decreased by 32%.

Pre-Algebra 8-4 Percent Increase and Decrease A. When Jeff was watching TV, the number of times his eyelids blinked went from 50 blinks per minute to 75 blinks per minute. What was the percent increase? Try This: Example 2A Think: What percent is 25 of 50? Set up the ratio. 75 – 50 = 25First find the amount of change. amount of increase original amount

Pre-Algebra 8-4 Percent Increase and Decrease = 50%Write as a percent. = 0.5Find the decimal form The blinking of Jeff’s eyelids increased by 50% when he watched TV. Try This: Example 2A Continued

Pre-Algebra 8-4 Percent Increase and Decrease B. In 2000, a certain stock was worth $9.00 a share. In 2003, the same stock was worth $3.80 a share. What was the percent decrease? Try This: Example 2B 9.00 – 3.80 = 5.20First find the amount of change. Think: What percent is 5.20 of 9.00? amount of decrease original amount Set up the ratio.

Pre-Algebra 8-4 Percent Increase and Decrease The value of the stock decreased by about 57.8% = 0.57Find the decimal form. = 57.7%Write as a percent. Try This: Example 2B Continued

Pre-Algebra 8-4 Percent Increase and Decrease A. Sarah bought a DVD player originally priced at $450 that was on sale for 20% off. What was the sale price? Additional Example 3A: Percent Increase and Decrease $450  20%First find 20% of $450. $450  0.20 = $9020% = 0.20 The amount of decrease is $90. Think: The reduced price is $90 less than $450. $450 – $90 = $360Subtract the amount of decrease. The sale price of the DVD player was $360.

Pre-Algebra 8-4 Percent Increase and Decrease A. Lily bought a dog house originally priced at $750 that was on sale for 10% off. What was the sale price? Try This: Example 3A $750  10%First find 10% of $750. $750  0.10 = $7510% = 0.10 The amount of decrease is $75. Think: The reduced price is $75 less than $750. $750 – $75 = $675Subtract the amount of decrease. The sale price of the dog house was $675.

Pre-Algebra 8-4 Percent Increase and Decrease 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? Additional Example 3B: Percent Increase and Decrease $85  40% First find 40% of $85. $85  0.40 = $3440% = 0.40 The amount of increase is $34. Think: The retail price is $34 more than $85. $85 + $34 = $119 Add the amount of increase. The retail price of this printer will be $119.

Pre-Algebra 8-4 Percent Increase and Decrease B. Barb has a grocery store in which she sells everything at 50% above the wholesale price. If she purchased a prime rib for $30 wholesale, what will be the retail price? $30  50% First find 50% of $30. $30  0.50 = $1550% = 0.50 The amount of increase is $15. Think: The retail price is $15 more than $30. $30 + $15 = $45Add the amount of increase. The retail price of the prime rib will be $45. Try This: Example 3B

Pre-Algebra 8-4 Percent Increase and Decrease Textbook Classwork Due at the end of the period! You may work with ONE other person! Page 414 #1-17

Pre-Algebra 8-4 Percent Increase and Decrease Lesson Quiz Find each percent increase or decrease to the nearest percent. 1. from 12 to from 1625 to from 37 to from 1.25 to A computer game originally sold for $40 but is now on sale for 30% off. What is the sale price of the computer game? 14% decrease 25% increase 238% increase 32% decrease $28