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A population, currently 200 , is growing at \(5 \%\) per year. (a) Write a formula for the population, \(P\), as a function of time, \(t\), years in the future. (b) Graph \(P\) against \(\bar{t}\). (c) Estimate the population 10 years from now. (d) Use the graph to estimate the doubling time of the population.

Short Answer

Expert verified
(a) \( P(t) = 200(1.05)^t \). (b) Graph: exponential. (c) 326 people. (d) Doubling time \( \approx 14.21 \) years.

Step by step solution

01

Understanding Exponential Growth

Initially, we know the population is growing at a rate of 5% per year. Exponential growth can be modeled with the formula \[ P(t) = P_0 (1 + r)^t \]where \( P_0 \) is the initial population, \( r \) is the growth rate as a decimal, and \( t \) is time in years.
02

Writing the Formula

Given that the initial population \( P_0 = 200 \) and the growth rate \( r = 0.05 \), the population formula is:\[ P(t) = 200(1.05)^t \]
03

Graphing the Function

To graph \( P(t) = 200(1.05)^t \), you can use a graphing tool or software. Plot the time \( t \) on the x-axis and the population \( P \) on the y-axis. This will give a curve that shows exponential growth.
04

Estimating Population in 10 Years

To find the population 10 years from now, substitute \( t = 10 \) into the formula:\[ P(10) = 200(1.05)^{10} \]Calculating this gives:\[ P(10) \approx 200 \times 1.62889 \approx 325.78 \]Thus, the estimated population in 10 years is approximately 326.
05

Estimating Doubling Time from the Graph

On the graph, find the point where the population doubles from 200 to 400. The doubling time can be estimated by observing the time \( t \) at which the graph reaches 400. For a 5% growth rate, the doubling time is approximately 14.21 years, typically derived using \( t = \frac{\log(2)}{\log(1.05)} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Population Modeling
Population modeling is an essential mathematical tool used to describe how populations change over time. By using models such as exponential growth, we can predict future populations based on current data.
In the given problem, we are tasked with modeling a population of 200 that grows by 5% annually. To achieve this, we employ an exponential growth formula. This formula allows us to see how the population will increase over time.
Population modeling can be utilized in various fields, including ecology, economics, and urban planning, to forecast changes and make informed decisions. With precise data and correct models, such as the one given by the formula \( P(t) = P_0 (1 + r)^t \), understanding population dynamics becomes more tangible.
Growth Rate
The growth rate is a fundamental concept that indicates how quickly a population increases over time. In this exercise, the population grows at a rate of 5% per year. To use this in calculations, it's crucial to express it as a decimal, i.e., 0.05.
The exponential growth formula \( P(t) = P_0 (1 + r)^t \) incorporates the growth rate \( r \), showing its importance in the predictive equation.
Understanding the growth rate lets us anticipate not just immediate changes, but also cumulative effects over extended periods. In real-world applications, interpreting growth rates can illuminate trends and help forecast future scenarios.
Doubling Time
Doubling time is the period required for a population to double in size. It’s a useful measure for understanding the pace of exponential growth.
In the context of our problem, the initial population is 200, and we are interested in finding out when it reaches 400 using a growth rate of 5%.
We can estimate the doubling time using the formula \( t = \frac{\log(2)}{\log(1 + r)} \). For this problem, it gives approximately 14.21 years.
Grasping the concept of doubling time is critical for long-term predictions, whether for populations, investments, or any setting involving exponential growth.
Graphing Functions
Graphing functions is a vital skill to visually interpret mathematical models, such as exponential growth. In this exercise, graphing the function \( P(t) = 200(1.05)^t \) involves plotting time \( t \) on the x-axis and population \( P \) on the y-axis.
The resulting graph typically presents a curve that illustrates how quickly the population grows over time, emphasizing the exponential nature of the increase.
By examining the graph, we can visually identify key points like the initial population and estimate values such as when the population doubles. Graphs provide an intuitive understanding that can reinforce analytical results, allowing users to see and verify patterns and trends effectively. Hence, creating and analyzing graphs supports deeper insights into the dynamics of growth models.

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