USING PERCENTS AND CALCULATING PERCENT CHANGE Objectives: SWBAT do calculations using percents. SWBAT find percents of increase and decrease. SWBAT use percent change to find initial or final values.

Percents A percent is a ratio out of 100. Example: In the Uplift class of 2012, about 64% of the students are female. If there are 96 students in the class, how many girls are there? 64 = x 64*96 = 100 x 100 96 6144 = 100 x 61. 44 = x There are 61 girls in the class.

Ex. : State whether each percent of change is a percent of decrease or increase. Then find the percent of change. 1. initial: 32 final: 40 2. initial: 20 final: 4 40 – 32 = 8 4 – 20 = -16 8 = 0. 25 -> 25% 32 -16 = - 0. 8 = -80% 20

Vocabulary Percent: a fraction out of 100 Percent of change: an increase or decrease expressed at a percent. Percent of increase: the percent by which new number is greater than the original number. Percent of decrease: the percent by which the new number is less than the original number.

Percent of Change Formula Percent of Change: final amount – initial amount

You TRY!!!! 3. initial: 72 final: 36 36 – 72 = - 36 -36 = -0. 5 = - 50% 72 4. initial: 45 final: 50 50 – 45 = 5 5 = 0. 111 = 11. 1% 45

Using Percent Change To calculate final value, use (1 + c) * initial value. c = % change written as a decimal Example: A store is having a 20% off sale. How much does a shirt that was $60 cost? Initial value: $60 Percent change: -20% = -. 2 (1 + -. 2) * $60 = 0. 8 * $60 = $48

Ex: Using Percent Change 1. The price a used-book store pays to buy a book is $5. The store sells the book for 28% above the price that it pays for the book. What is the selling price of the $5 book?

Ex: Find the total price of each item. 1. Software: $39. 50 Sales tax: 6. 5% 2. $15. 99 sales tax: 5. 75% Compact disc:

Ex: Find the discounted price of each item. 1. jeans: $45. 00 discount: 25% 2. book: $19. 95 discount: 33%

Ex: Find the final price of each 1. lamp: $120. 00 discount: 20% tax: 6% 2. camera: $58. 00 discount: 25% tax: 6. 5%

Practice In 1987, the United States had 2 million active-duty military personnel. By 2000, there were only 1. 4 million active-duty military personnel. What was the percent of decrease?

Practice In order for a food to marked “reduced fat, ” it must have at least 25% less fat than the same full-fat food. If one ounce of reduced fat chips has 6 grams of fat, what is the least amount of fat in one ounce of regular chips?