Populations are effected by the birth and death rate, as well as the number of people who move in and out each year. 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 displays the size of a population for any number of years. The program should ask for the following data: • The starting size of a population
• The annual birth rate
• The annual death rate
• The number of years to display
Write a function that calculates the size of the population for a year. The formula is
N = P + BP − DP
where N is the new population size, P is the previous population size, B is the birth rate, and D is the death rate.
Input Validation: Do not accept numbers less than 2 for the starting size. Do not accept negative numbers for birth rate or death rate. Do not accept numbers less than 1 for the number of years.
#include
using namespace std;
double calcOfPopulation(double, double, double);
double inputValidate(double, int);
int main()
{
double P, // population size
B, // birth rate %
D, // death rate %
num_years;
cout << "Starting size of population: ";
P = inputValidate(P, 2);
cout << "Annual birth rate: %";
B = inputValidate(B, 0);
cout << "Annual death rate: %";
D = inputValidate(D, 0);
cout << "Number of years to display: ";
num_years = inputValidate(num_years, 1);
cout << "Population size for "
<< num_years << " years "
<< " = "
<< (calcOfPopulation(P, B, D) * num_years)
<< endl;
return 0;
} // END int main()
double inputValidate(double number, int limit)
{
while(!(cin >> number) || number < limit)
{
cout << "Error. Number must not be "
<< " 0 or greater:";
cin. clear();
cin. ignore(numeric_limits::max(), '\n');
}
return number;
}
double calcOfPopulation(double P, double B, double D)
{
B *= .01; // 3.33% = .0333
D *= .01; // 4.44% = .0444
return P + (B * P) - (D * P);