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Using Percents and Calculating Percent Change

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.

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Using Percents and Calculating Percent Change

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  1. 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.

  2. 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 = 100x 100 96 6144 = 100x 61.44 = x There are 61 girls in the class.

  3. Ex. : State whether each percent of change is a percent of decrease or increase. Then find the percent of change. • initial: 32 final: 40 40 – 32 = 8 8 = 0.25 -> 25% 32 • initial: 20 final: 4 4 – 20 = -16 -16 = - 0.8 = -80% 20

  4. 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.

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

  6. You TRY!!!! • initial: 72 final: 36 36 – 72 = - 36 -36 = -0.5 = - 50% 72 • initial: 45 final: 50 50 – 45 = 5 5 = 0.111 = 11.1% 45

  7. 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

  8. Ex: Using Percent Change • 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?

  9. Ex: Find the total price of each item. 1. Software: $39.50 Sales tax: 6.5% • Compact disc: $15.99 sales tax: 5.75%

  10. Ex: Find the discounted price of each item. • jeans: $45.00 discount: 25% • book: $19.95 discount: 33%

  11. Ex: Find the final price of each • lamp: $120.00 discount: 20% tax: 6% • camera: $58.00 discount: 25% tax: 6.5%

  12. 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?

  13. 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?

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