The population of a certain country is known to increase at

abreviatsjw

abreviatsjw

Answered question

2022-01-03

The population of a certain country is known to increase at a rate proportional to the number of people presently living in the country. If after two years the population has doubled, and after three years the population is 20,000. Estimate the initial population of the nation and find an expression for the country's approximate population at any time.

Answer & Explanation

sirpsta3u

sirpsta3u

Beginner2022-01-04Added 42 answers

Given that the number of people living there now determines how quickly the population of the country grows,
dP dt =kP, where P is the population 
k is the proportionality constant 
1pdP=k dt  
lnP=kt+C 
Let P0 be the population initially 
t=0P=P0 
P=P0ekt 
Given that at 2 years the population is dobuled 
2=e2k 
k=ln(2) 
Given that at 3 years the population is 20000 
20000=Pie3ln2 
Therefore the equation is P=P0eln(2)2t

Paul Mitchell

Paul Mitchell

Beginner2022-01-05Added 40 answers

Rate of increase of population is proportional to Number of people living presently
After 2 years, Population has doubled
After 3 years, Population =20000
Let P be population in the country.
Thus, according to the question:
dPdtP
dPdt=kP, where k is any constant.
dPP=k.dt
dPP=k.dt
lnP=k.t+C
When t=0 years, P=P0, where P0 is the initial population.
Thus, lnP0=0+C
C=lnP0
lnP=kt+lnP0
lnPlnP0=kt
ln(PP0)=kt
When t=2 years, P=2P0
ln(2P0P0)=kx2
k=ln22
ln(PP0)=ln22.t
When t=3 years, P=20000
ln(20000P0)=ln22x3
ln(20000P0)=1.0397
20000P0=e1.0397
P0=20000e1.0397=7071.2
P0=7072
So, initial population, P0=7072
karton

karton

Expert2022-01-09Added 613 answers

Let make N represent the population of the country at any given time t and No as the initial population.
dNdt=kN
where k is the constant of proportionality.
1NdN=kdt
lnN=kt+C
For t=0,N=No
Therefore, N=Noekt (1)
For t=2 yrs, N=2No
Substitute these values into (1)
2No=Noe2t
k=12ln2
k=0.347
Therefore (1) becomes
N=Noe0.347t (2)
For t=3 yrs, N=20,000
Substitute these values into (2)
20000=Noe0.347(3)
No=20000e0.347(3)
No=7062
Therefore the number of people initially living in the country is 7062

madeleinejames20

madeleinejames20

Skilled2023-06-14Added 165 answers

Given that the population increases at a rate proportional to the number of people presently living in the country, we can express this relationship with the differential equation:
dPdt=kP
Where k is the proportionality constant. This is a separable differential equation, so we can solve it by separating variables and integrating:
1PdP=kdt
Integrating both sides gives:
ln|P|=kt+C
Where C is the constant of integration. Applying the initial condition that after two years the population has doubled, we have:
ln|2P0|=2k+C
Simplifying, we get:
C=ln|2P0|2k
Now, using the second condition that after three years the population is 20,000, we have:
ln|20|=3k+C
Substituting the expression for C from above, we get:
ln|20|=3k+ln|2P0|2k
Simplifying further:
ln|20|ln|2P0|=k
Applying the logarithmic identity ln(a)ln(b)=ln(ab), we have:
ln(202P0)=k
Now, to find the value of P0, we substitute this value of k into the first equation we obtained:
ln|P|=kt+C
Using the initial condition P(3)=20, we have:
ln|20|=k(3)+C
Substituting the value of k we found earlier:
ln|20|=ln(202P0)(3)+C
Simplifying:
ln|20|=3ln(202P0)+C
Applying the logarithmic identity ln(ab)=bln(a), we have:
ln|20|=ln(20(2P0)3)+C
Using the logarithmic identity ln(ab)=ln(a)ln(b), we get:
ln|20|=ln(208P03)+C
Applying the logarithmic identity ln(ea)=a, we have:
ln|20|=ln(208P03)+C
Therefore, the expression for the country's approximate population at any time t is:
P(t)=ekt+C where k and C are determined as shown above.
To estimate the initial population of the nation, we substitute t=0 into the expression:
P(0)=ek(0)+C=eC
Given the value of ln|20| calculated earlier, we can write the expression for the initial population as:
P0=208eln|20|
Therefore, the initial population of the nation is approximately 208eln|20| thousand people.
Eliza Beth13

Eliza Beth13

Skilled2023-06-14Added 130 answers

Let's denote the initial population of the country as P0. According to the given information, we know that after two years the population has doubled, so the population after two years is 2P0.
We are also told that after three years, the population is 20,000. Let's denote the population after three years as P3.
We can set up a proportion to solve for P0:
2P0P3=P020000
To solve this proportion, we can cross-multiply:
2P0×20000=P0×P3
Simplifying further, we have:
40000P0=P0P3
Dividing both sides by P0, we get:
40000=P3
Therefore, the population after three years is 40,000.
To find the initial population of the nation, we substitute the value of P3 back into one of the previous equations. Let's use the equation from after two years:
2P0=40000
Dividing both sides by 2, we find:
P0=20000
Therefore, the initial population of the nation is 20,000.
Now, let's find an expression for the country's approximate population at any time, t. We can use the exponential growth formula:
P(t)=P0ekt
Where:
- P(t) is the population at time t
- P0 is the initial population
- k is the constant of proportionality
Since we know that the population doubles after two years, we can use this information to find the value of k. Let's substitute the values into the equation:
2P0=P0e2k
Dividing both sides by P0, we get:
2=e2k
Taking the natural logarithm of both sides, we have:
ln(2)=2k
Dividing both sides by 2, we find:
k=ln(2)2
Now we can substitute this value of k into the equation for P(t):
P(t)=P0eln(2)2t
Therefore, the expression for the country's approximate population at any time t is P(t)=20000eln(2)2t.

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