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  1. //Cameron Pham             CS1A                       Chapter 6, p. 373, #15
  2. //
  3. /******************************************************************************
  4. * CALCULATE POPULATION SIZE
  5. * ______________________________________________________________________________
  6. * This program accepts an integer value for the starting size of a population,
  7. * number of years, and floating point values for the annual birth and death 
  8. * rate.
  9. * ______________________________________________________________________________
  10. * INPUT
  11. * Population size		// Starting size of population
  12. * Annual birth rate 	// Yearly rate at which people are born
  13. * Annual death rate		// Yearly rate at which people pass away
  14. * Years					// Period of time to calculate population 
  15. * 
  16. * OUTPUT
  17. * Size of population	// Calculated size of a population after given years
  18. * 
  19. *******************************************************************************/
  20. #include <iostream>
  21. #include <iomanip>
  22. using namespace std;
  23.  
  24. // Function prototype
  25. double calculatePopulation(double population, double birthRate, 
  26. double deathRate);
  27.  
  28. int main()
  29. {
  30.     // Declare variables
  31.     double population;
  32.     double birthRate;
  33.     double deathRate;
  34.     int years;
  35.  
  36.     // Get the starting population
  37.     cout << "Enter the starting population size: ";
  38.     cin >> population;
  39.     cout << endl;
  40.  
  41.     // Validate the starting population
  42.     while (population < 2)
  43.     {
  44.         cout << "Population must be at least 2. Enter again: ";
  45.         cin >> population;
  46.     }
  47.  
  48.     // Get the annual birth and death rates
  49.     cout << "Enter the annual birth rate (percentage): ";
  50.     cin >> birthRate;
  51.      cout << endl;
  52.  
  53.     cout << "Enter the annual death rate (percentage): ";
  54.     cin >> deathRate;
  55.      cout << endl;
  56.  
  57.     // Get the number of years
  58.     cout << "Enter the number of years to display: ";
  59.     cin >> years;
  60.      cout << endl;
  61.  
  62.     // Validate the number of years
  63.     while (years < 1)
  64.     {
  65.         cout << "Years must be at least 1. Enter again: ";
  66.         cin >> years;
  67.     }
  68.  
  69.     // Convert percentages to decimal rates
  70.     birthRate /= 100.0;
  71.     deathRate /= 100.0;
  72.  
  73.     // Display the population 
  74.  
  75.     cout << fixed << setprecision(2);
  76.     population = calculatePopulation(population, birthRate, deathRate);
  77.     cout << years << " year(s): " << population << " people." << endl;
  78.  
  79.  
  80.     return 0;
  81. }
  82.  
  83. // Function to calculate the new population size
  84. double calculatePopulation(double population, double birthRate, 
  85. double deathRate)
  86. {
  87.     double newPopulation;
  88.  
  89.     newPopulation = population + birthRate * population - deathRate * population;
  90.  
  91.     return newPopulation;
  92. }
Success #stdin #stdout 0s 5320KB
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5000 0.80 0.90 10
stdout
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Enter the starting population size: 
Enter the annual birth rate (percentage): 
Enter the annual death rate (percentage): 
Enter the number of years to display: 
10 year(s): 4995.00 people.
https://ideone.com/CwBYsC
Chapter 6, p. 373, #15
language:
C++ (gcc 8.3)
created:
7 days ago
visibility:
public

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