Over the next 10 years, town A is expecting to gain 1000 people each year. During the same time period, the population of town B is expected to increase by 5% each year. Both town A and town B currently have populations of 10,000 people. The table below shows the expected population of each town for the next three years.Which number of years is the best approximation of the time until town A and town B once again have the same population?

Over the next 10 years, town A is expecting to gain 1000 people each year. During the same time period, the population of town B is expected to increase by 5% e class=

Answer :

From the given figure we can see

The population in town A is increased by a constant rate because

[tex]\begin{gathered} 11000-10000=1000 \\ 12000-11000=1000 \\ 13000-12000=1000 \end{gathered}[/tex]

Since the difference between every 2 consecutive terms is the same, then

The rate of increase of population is constant and = 1000 people per year

The form of the linear equation is

[tex]y=mx+b[/tex]

m = the rate of change

b is the initial amount

Then from the information given in the table

m = 1000

b = 10,000

Then the equation of town A is

[tex]y=1000t+10000[/tex]

Fro town B

[tex]\begin{gathered} R=\frac{10500}{10000}=1.05 \\ R=\frac{11025}{10500}=1.05 \\ R=\frac{11576}{11025}=1.05 \end{gathered}[/tex]

Then the rate of increase of town by is exponentially

The form of the exponential equation is

[tex]y=a(R)^t[/tex]

a is the initial amount

R is the factor of growth

t is the time

Since R = 1.05

Since a = 10000, then

The equation of the population of town B is

[tex]y=10000(1.05)^t[/tex]

We need to find t which makes the population equal in A and B

Then we will equate the right sides of both equations

[tex]10000+1000t=10000(1.05)^t[/tex]

Let us use t = 4, 5, 6, .... until the 2 sides become equal

[tex]\begin{gathered} 10000+1000(4)=14000 \\ 10000(1.05)^4=12155 \end{gathered}[/tex][tex]\begin{gathered} 10000+1000(5)=15000 \\ 10000(1.05)^5=12763 \end{gathered}[/tex][tex]\begin{gathered} 10000+1000(6)=16000 \\ 1000(1.05)^6=13400 \end{gathered}[/tex][tex]\begin{gathered} 10000+1000(30)=40000 \\ 10000(1.05)^{30}=43219 \end{gathered}[/tex]

Since 43219 approximated to ten thousand will be 40000, then

A and B will have the same amount of population in the year 30

The answer is year 30

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