The formula A=23.1e^.0153t models the population of a US state, A, in millions, t years after 2000
a. What was the population of the state in 2000?
b.When will the population of the state reach 28.3 million?

Respuesta :

Part A

Plug t = 0 into the function to find the population in the year 2000.

This works because t represents the number of years since 2000.

So t = 0 represents 2000, t = 1 is 2001, t = 2 is 2002, and so on.

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A = 23.1*e^(0.0153*t)

A = 23.1*e^(0.0153*0)

A = 23.1*e^(0)

A = 23.1*1

A = 23.1

Recall that the variable A is the population in millions.

Saying A = 23.1 is saying there are 23.1 million people (ie 23 million, 100 thousand)

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Answer: 23.1 million

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Part B

Replace A with 28.3 and use natural logarithms to isolate t.

We'll use the log rules Ln(e) = 1 and Ln(x^y) = y*Ln(x).

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A = 23.1*e^(0.0153*t)

28.3 = 23.1*e^(0.0153*t)

23.1*e^(0.0153*t) = 28.3

e^(0.0153*t) = 28.3/23.1

e^(0.0153*t) = 1.22510822510822

Ln[ e^(0.0153*t) ] = Ln[ 1.22510822510822 ]

0.0153*t*Ln[ e ] = Ln[ 1.22510822510822 ]

0.0153*t*1 = Ln[ 1.22510822510822 ]

0.0153*t = Ln[ 1.22510822510822 ]

t = Ln[ 1.22510822510822 ]/0.0153

t = 13.2698815112052

It will take approximately 13.2699 years for the population to reach the desired target.

This result is between 13 and 14.

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Answer: Between 2013 and 2014

We want to study the population formula of a given US state.

a) 23.1 millions.

b) in 2013 - 2014

The population state is:

A = 23.1*e^(0.0153*t)

In millions.

Where t represents the number of years after 2000.

a) For the population at the year 2000, we need to evaluate the function at t = 0 (2000 is 0 years after 2000).

A(0) = 23.1*e^(0.0153*0) = 23.1

The population at year 2000 was 23.1 millions.

b) Now we want to solve:

A(t) = 28.3 = 23.1*e^(0.0153*t)

         28.3/23.1 = e^(0.0153*t)

         1.23 = e^(0.0153*t)

Now we can apply the natural logarithm to both sides:

ln(1.23) = ln( e^(0.0153*t) )

ln(1.23) = 0.0153*t

ln(1.23)/0.0153 = t = 13.5

So 13.5 years after 2000 the population will be 28.3 million.

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