The formula [tex]A = 24.2 e^{0.0788 t}[/tex] models the population of a US state, [tex]A[/tex], in millions, [tex]t[/tex] years after 2000.

a. What was the population of the state in 2000?

b. When will the population of the state reach 31.4 million?

a. In 2000, the population of the state was [tex]\square[/tex] million.



Answer :

To answer the questions based on the given population model formula [tex]\( A = 24.2 e^{0.0788 t} \)[/tex], let's go through each part step by step.

### Part (a)
The population model is given by:
[tex]\[ A = 24.2 e^{0.0788 t} \][/tex]
where [tex]\( A \)[/tex] is the population in millions and [tex]\( t \)[/tex] is the number of years after 2000.

In 2000, [tex]\( t = 0 \)[/tex].

Substituting [tex]\( t = 0 \)[/tex] into the formula, we get:
[tex]\[ A = 24.2 e^{0.0788 \cdot 0} \][/tex]

Next, calculate the exponent:
[tex]\[ 0.0788 \cdot 0 = 0 \][/tex]

Therefore, the equation simplifies to:
[tex]\[ A = 24.2 e^0 \][/tex]

Since [tex]\( e^0 = 1 \)[/tex]:
[tex]\[ A = 24.2 \cdot 1 \][/tex]
[tex]\[ A = 24.2 \][/tex]

Thus, in 2000, the population of the state was 24.2 million.

### Part (b)
We need to determine when the population of the state will reach 31.4 million. This means we need to solve for [tex]\( t \)[/tex] when [tex]\( A = 31.4 \)[/tex].

Starting with the formula:
[tex]\[ 31.4 = 24.2 e^{0.0788 t} \][/tex]

First, isolate the exponential term by dividing both sides of the equation by 24.2:
[tex]\[ \frac{31.4}{24.2} = e^{0.0788 t} \][/tex]
[tex]\[ 1.2975206611570248 \approx e^{0.0788 t} \][/tex]

To solve for [tex]\( t \)[/tex], take the natural logarithm (ln) of both sides:
[tex]\[ \ln(1.2975206611570248) = \ln(e^{0.0788 t}) \][/tex]

Using the property of logarithms, [tex]\( \ln(e^x) = x \)[/tex]:
[tex]\[ \ln(1.2975206611570248) = 0.0788 t \][/tex]

Next, solve for [tex]\( t \)[/tex] by dividing both sides by 0.0788:
[tex]\[ t = \frac{\ln(1.2975206611570248)}{0.0788} \][/tex]

Evaluating the division, we obtain the approximate number of years:
[tex]\[ t \approx 3.3052697938016107 \][/tex]

Thus, it will take approximately 3.31 years for the population of the state to reach 31.4 million.