/***********************************************************
birth-deathrate.ch
Populations Word Problem
Use this program to help students determine how long it
will take to reach a certain target population, given a
starting population, birthrate, and death rate. Have
students analyze, fill in parts of, or use the program
to check results to exercises they are already working on
************************************************************
Copyright 2014 SoftIntegration Inc.
http://www.softintegration.com
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
***********************************************************/
// constants are predefined here
#define POPULATION 10000000.0
#define BIRTHRATE 0.015
#define DEATHRATE 0.023
#define REDUCTION 0.1
// initialize variables used for program
int current_pop, target_pop, years, change_pop;
current_pop = POPULATION;
target_pop = POPULATION * REDUCTION;
years = 0;
change_pop = 0.0;
// Determines the number of years to reach the target population
while (current_pop >= target_pop)
{
change_pop = (current_pop * BIRTHRATE) - (current_pop * DEATHRATE);
current_pop = current_pop + change_pop;
years = years + 1;
}
// Prints the answer
printf("Number of years until target population reached: %d\n", years);