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The formula [tex]\( A = 21.2 e^{0.0407 t} \)[/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 29.8 million?

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

b. The population of the state will reach 29.8 million in the year [tex]\(\square\)[/tex].

(Round down to the nearest year.)


Sagot :

Certainly! Let's solve the problem step-by-step.

### Part (a)
We need to find out the population of the state in the year 2000. The given formula for population is:

[tex]\[ A = 21.2 \cdot e^{0.0407t} \][/tex]

Here, [tex]\( A \)[/tex] is the population in millions, and [tex]\( t \)[/tex] is the number of years after 2000. For the year 2000, [tex]\( t = 0 \)[/tex].

Substitute [tex]\( t = 0 \)[/tex] into the formula:

[tex]\[ A = 21.2 \cdot e^{0.0407 \cdot 0} \][/tex]
[tex]\[ A = 21.2 \cdot e^0 \][/tex]
[tex]\[ A = 21.2 \cdot 1 \][/tex]
[tex]\[ A = 21.2 \][/tex]

So, the population of the state in 2000 was [tex]\( 21.2 \)[/tex] million.

### Part (b)
We need to find out when the population of the state will reach 29.8 million. That means we need to find the value of [tex]\( t \)[/tex] when [tex]\( A = 29.8 \)[/tex].

Starting with the equation:

[tex]\[ 29.8 = 21.2 \cdot e^{0.0407t} \][/tex]

Solve for [tex]\( t \)[/tex] by isolating the exponential term:

[tex]\[ \frac{29.8}{21.2} = e^{0.0407t} \][/tex]

Take the natural logarithm (ln) of both sides to solve for [tex]\( t \)[/tex]:

[tex]\[ \ln\left(\frac{29.8}{21.2}\right) = 0.0407t \][/tex]

[tex]\[ t = \frac{\ln\left(\frac{29.8}{21.2}\right)}{0.0407} \][/tex]

Calculating the value gives approximately [tex]\( t = 8 \)[/tex].

Since [tex]\( t \)[/tex] represents the number of years after 2000, the year when the population will reach 29.8 million is:

[tex]\[ 2000 + 8 = 2008 \][/tex]

### Final Answers
a. In 2000, the population of the state was [tex]\( \boxed{21.2} \)[/tex] million.
b. The population of the state will reach 29.8 million in the year [tex]\( \boxed{2008} \)[/tex].