the number of people living in a country is increasing each year exponentially so that the number of people 5 years ago was 4 million. the number of people in five years time is projected to be 6.25 million. what is the present population of the country?

Respuesta :

Using an exponential function, it is found that the present population of the country is of 5 million.

What is an exponential function?

It is modeled by:

[tex]P(t) = P(0)e^{rt}[/tex]

In which P(0) is the initial value and r is the growth rate, as a decimal.

Considering five years ago as the first year, we have that P(0) = 4, P(10) = 6.25, hence this is used to find r.

[tex]P(t) = P(0)e^{rt}[/tex]

[tex]6.25 = 4e^{10r}[/tex]

[tex]e^{10r} = 1.5625[/tex]

[tex]\ln{e^{10r}} = \ln{1.5625}[/tex]

[tex]10r = \ln{1.5625}[/tex]

[tex]r = \frac{\ln{1.5625}}{10}[/tex]

[tex]r = 0.044629[/tex]

Then, the equation is:

[tex]P(t) = 4e^{0.044629t}[/tex]

The present moment is five years from the beginning, hence:

[tex]P(5) = 4e^{0.044629 \times 5} = 5[/tex]

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The present population of the country is 4.9 million people

How to determine the present population?

Let x represent the number of years and y represents the population.

So, we have the following points:

(x,y) = (-5,4 million) and (5,6.25 million)

An exponential function is represented as:

[tex]y = ab^x[/tex]

So, we have:

[tex]4 = ab^{-5}[/tex]

[tex]6.25 = ab^{5}[/tex]

Divide both equations

[tex]b^{10} = 1.5626[/tex]

Take the 10th root of both sides

b = 1.05

Substitute b = 1.05 in [tex]6.25 = ab^{5}[/tex]

[tex]6.25 = a(1.05)^5[/tex]

Evaluate the exponent

6.25 = 1.276a

Divide both sides by 1.276

a = 4.9

Hence, the present population of the country is 4.9 million people

Read more about exponential functions at:

https://brainly.com/question/11464095

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