A population P satisfies dP/dt = 0.04P and has an initial population of 500. Find P(t) and determine the population after 10 years.
Solution
Problem
Step 1: Recognize the exponential growth model.
The differential equation is:
dP/dt = 0.04P
An equation of the form dP/dt = kP has the general solution:
P(t) = Ce^(kt)
Here:
k = 0.04
So:
P(t) = Ce^(0.04t)
Step 2: Apply the initial condition.
The initial population is 500, so:
P(0) = 500
Substitute t = 0:
500 = Ce^(0)
Since e^0 = 1:
C = 500
Step 3: Write the population model.
P(t) = 500e^(0.04t)
Step 4: Find the population after 10 years.
Substitute t = 10:
P(10) = 500e^(0.04 × 10)
P(10) = 500e^0.4
Step 5: Approximate the value.
e^0.4 ≈ 1.49182
Therefore:
P(10) ≈ 500(1.49182)
P(10) ≈ 745.91
Step 6: Interpret the result.
A population is normally expressed as a whole number, so the model predicts approximately 746 individuals after 10 years.
Therefore, P(t) = 500e^(0.04t), and P(10) ≈ 746.
Result
P(t) = 500e^(0.04t); P(10) ≈ 746