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Percents

Percents. MATH 102 Contemporary Math S. Rook. Overview. Section 9.1 in the textbook: Percents Percent of change Percent equation. Percents. Percents. Percents are used in many applications: e.g. Interest rate, credit card rate, scores Percent means per 100

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Percents

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  1. Percents MATH 102 Contemporary Math S. Rook

  2. Overview • Section 9.1 in the textbook: • Percents • Percent of change • Percent equation

  3. Percents

  4. Percents • Percents are used in many applications: • e.g. Interest rate, credit card rate, scores • Percent means per 100 • e.g. 23% means 23 per 100 or 23⁄100 • To convert a percent to a decimal: • Drop the percent sign and move the decimal point two places to the left • To convert a decimal to a percent: • Move the decimal point two places to the right and append a percent sign

  5. Percents (Continued) • To convert a fraction to a percent: • Recall that the fraction bar indicates division • Either use long division or a calculator to convert the fraction into a decimal • Convert the decimal to a percent • You MUST understand how to convert to percents and from percents!

  6. Percents (Example) Ex 1: Convert: a) 0.35% to a decimal b) 0.423 to a percent c) 4⁄250 to a percent

  7. Percent of Change

  8. Percent Change • Percents can be used to indicate change from a past observation to a new observation • If the new observation is greater than the past observation, there has been a percent increase • If the past observation is greater than the new observation, there has been a percent decrease • The percent change is always relative to the past observation

  9. Percent Change (Example) Ex 2: Find the percent change and indicate whether it is an increase or decrease: a) The HCC student population was approximately 3000 in 2000 and is approximately 8000 in 2010. b) A cake originally priced at $11.00 is marked down to $5.00.

  10. Percent Equation

  11. Percent Equation • Most percent problems can be solved using the following equation: percent x base = amount • The percent is usually converted to a decimal when used in calculations • The base can sometimes be considered the whole • Usually preceded by the word “of” • The amount can sometimes be considered the part

  12. Percent Equation (Example) Ex 3: Solve: a) 12 is what percent of 80? b) 77 is 22% of what number? c) What is 12.25% of 160?

  13. Percent Equation (Example) Ex 4: In a recent year, the top-selling cookie in America was Nabisco’s Chips Ahoy with sales of $294.6 million. The total cookie sales for that year were $3,124 million. What percent of the total cookie sales were due to Chips Ahoy?

  14. Percent Equation (Example) Ex 5: According to the U.S. Bureau of the Census, from 2005 to 2006, the average price of a new home in the Northeast increased by 7.88% to $428,000. What was the average price of a new home in the Northeast in 2005 – round the answer to the nearest thousand.

  15. Percent Equation (Example) Ex 6: Jed works for Metal Fabricators Inc. which just lost a large contract and has asked employees to take a pay cut. If Jed now makes $34,500 per year before the pay cut and $30,360 afterwards, what percent was his pay cut?

  16. Summary • After studying these slides, you should know how to do the following: • Convert to and from percents • Calculate percent change • Solve application problems involving percent • Additional Practice: • See problems in Section 9.1 • Next Lesson: • Interest (Section 9.2)

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