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Advanced Math / Nonlinear functions Difficulty: Medium

A model predicts that the population of Bergen was 15,000 in 2005. The model also predicts that each year for the next 5 years, the population p  increased by 4% of the previous year's population. Which equation best represents this model, where x  is the number of years after 2005, for x5?

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Explanation

Choice D is correct. It's given that a model predicts the population of Bergen in 2005 was 15,000 . The model also predicts that each year for the next 5 years, the population increased by 4% of the previous year's population. The predicted population in one of these years can be found by multiplying the predicted population from the previous year by 1.04 . Since the predicted population in 2005 was 15,000 , the predicted population 1 year later is 15,000(1.04). The predicted population 2 years later is this value times 1.04 , which is 15,0001.041.04, or 15,0001.042. The predicted population 3 years later is this value times 1.04 , or 15,0001.043. More generally, the predicted population, p , x years after 2005 is represented by the equation p=15,0001.04x

Choice A is incorrect. Substituting 0 for x in this equation indicates the predicted population in 2005 was 0.96 rather than 15,000 .

Choice B is incorrect. Substituting 0 for x in this equation indicates the predicted population in 2005 was 1.04 rather than 15,000 .

Choice C is incorrect. This equation indicates the predicted population is decreasing, rather than increasing, by 4% each year.