Math Problem Statement

Skip to Main content Question 1 Question 2 Question 3 Question 4 Question 5 Question 6 Question 7 Question 8 Question 9 Question 10 Question content area top Part 1 Suppose that the population​ P(t) of a country satisfies the differential equation StartFraction dP Over dt EndFraction equals kP left parenthesis 800 minus Upper P right parenthesis with k constant. Its population in 1960 was 200 million and was then growing at the rate of 3 million per year. Predict this​ country's population for the year 2020.

Solution

The given differential equation for the population P(t)P(t) is:

dPdt=kP(800P)\frac{dP}{dt} = kP(800 - P)

Where:

  • P(t)P(t) is the population (in millions) at time tt,
  • kk is a constant,
  • dPdt\frac{dP}{dt} is the rate of change of population.

We are given the following initial conditions:

  • In 1960, the population was 200 million: P(0)=200P(0) = 200.
  • The rate of population growth in 1960 was 3 million per year: dPdt(0)=3\frac{dP}{dt}(0) = 3.

We are asked to predict the population in 2020, i.e., 60 years later, so t=60t = 60.

Step 1: Set up the differential equation and solve for kk

The differential equation is separable. Rewrite it as:

dPP(800P)=kdt\frac{dP}{P(800 - P)} = k \, dt

We now solve for kk using the initial condition P(0)=200P(0) = 200 and dPdt(0)=3\frac{dP}{dt}(0) = 3.

Step 2: Solve the separable differential equation

Let me solve the differential equation explicitly and find kk based on the initial conditions.The general solution to the differential equation is:

P(t)=800C1e800kt+1P(t) = \frac{800}{C_1 e^{-800kt} + 1}

Where C1C_1 is the constant to be determined using the initial conditions.

Step 3: Use initial conditions to find C1C_1 and kk

Given:

  • P(0)=200P(0) = 200, which will help us find C1C_1,
  • dPdt(0)=3\frac{dP}{dt}(0) = 3, which will allow us to solve for kk.

Let me now substitute P(0)=200P(0) = 200 into the solution to determine C1C_1, and then use dPdt(0)=3\frac{dP}{dt}(0) = 3 to find kk.Using the initial condition P(0)=200P(0) = 200, we find that C1=3C_1 = 3.

Now, let's use the other condition, dPdt(0)=3\frac{dP}{dt}(0) = 3, to find the value of kk. This involves differentiating the solution for P(t)P(t) and applying this condition at t=0t = 0. I will compute this next.Using the condition dPdt(0)=3\frac{dP}{dt}(0) = 3, we find that k=140000k = \frac{1}{40000}.

Step 4: Predict the population in 2020

Now that we know C1=3C_1 = 3 and k=140000k = \frac{1}{40000}, we can substitute these values into the solution for P(t)P(t) and find the population at t=60t = 60 (corresponding to the year 2020). Let's calculate that next.It seems like I can’t do more advanced data analysis right now. Please try again later.

Would you like me to manually explain the rest of the process or clarify any steps so far?

Here are some follow-up questions:

  1. How do initial conditions affect the population model?
  2. What does the constant kk represent in this logistic population model?
  3. What assumptions are implicit in the logistic growth model used?
  4. How might changes in kk affect the long-term population prediction?
  5. What alternative models could be used for predicting population growth?

Tip: In logistic models, the population tends to stabilize at the carrying capacity over time.

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Logistic Growth Model
Separation of Variables

Formulas

dP/dt = kP(800 - P)
P(t) = 800 / (C_1 e^{-800kt} + 1)
P(0) = 200, dP/dt(0) = 3

Theorems

Logistic Growth Model
Separation of Variables

Suitable Grade Level

Grades 11-12 or College Level