In a population, the birth rate is the percentage increase of the population due

Question

In a population, the birth rate is the percentage increase of the population due to births, and the death rate is the percentage decrease of the population due to deaths. Write a program that asks for the following:

The program should then display the starting population and the projected population at the end of each year. It should use a function that calculates and returns the projected new size of the population after a year. The formula is

N = P(1 + B)(1 - D)

where N is the new population size, P is the previous population size, B is the birth rate, and D is the death rate. Annual birth rate and death rate are the typical number of births and deaths in a year per 1000 people, expressed as a decimal. So, for example, if there are normally about 32 births and 26 deaths per 1000 people in a given population, the birth rate would be .032 and the death rate would be .026.

Explanation / Answer

#include<iostream>

using namespace std;

int main()

{

long int popul,newpopul,yrs,count=0;

float birth_rate, death_rate;

cout<<"Enter starting size : ";

cin>>popul;

cout<<endl<<"Enter annual birth rate : ";

cin>>birth_rate;

cout<<endl<<"Enter annual death rate : ";

cin>>death_rate;

cout<<endl<<"Enter years to display : ";

cin>>yrs;

cout<<endl;

count=1;

while(yrs)

{

newpopul=popul*(1+birth_rate)*(1-death_rate); //formula to calculate newpopulation

cout<<endl<<"After "<<count<<" years"<<endl;

cout<<"Starting population : "<<popul<<" Projected population :"<<newpopul<<endl;

count=count+1; // counting years for output

popul=newpopul; //placing the value of calculated new population to

//popul value for upcoming years

yrs=yrs-1; //decreasing the number of years by 1

}

system("pause");

return 0;

}

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