Intermediate Algebra Section 9.7: Applications of Exponential and Logarithmic Functions 1. The number of skateboarders of age x , in thousands, can be approximated by x x N ) 9 .0 ( 1377 ) ( = , 60 7 ≤ ≤ x a. What does N represent? b. What does x represent? c. Estimate the number of 21 year old skaters? d. At what age are there only about 6,300 skaters? 2. The percentage of smokers who received telephone counseling and had successfully quit smoking for t months is given by t t P ) 914 .0 ( 4 . 21 ) ( = a. What does P represent? b. What does t represent? c. In what month will 15% of those who quit and used telephone counseling still be smoke free? 3. The world population, ) ( t P , in billions, t years after 1980 can be approximated by t t P ) 015 . 1 ( 495 . 4 ) ( = a. In what year will the world population reach 7 billion? b. Find the doubling time. The Exponential Growth Model: An exponential growth model is a function of the form: kt e P t P0 ) ( = , 0k , where 0P is the population at time 0,
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