problem return correct answers

Question

#include <cs50.h>
#include <stdio.h>

int main(void)
{
    int start, end, years = 0;
    // Prompt for start size
    do
    {
        start = get_int("Start size: ");
    }
    while (start < 9);
    // Prompt for end size
    do
    {
        end = get_int("End size: ");
    }
    while (end < start);
    //Calculating the number of years
    while (start < end)
    {
        start += (start / 2);
        years++;
    }
    printf("Years: %i\n", years);
}

output:

$ ./population
Start size: 1200
End size: 1300
Years: 1
$ ./population
Start size: -5
Start size: 3
Start size: 9
End size: 5
End size: 18
Years: 8
$ ./population
Start size: 20
End size: 1
End size: 10
End size: 100
Years: 20
$ ./population
Start size: 100
End size: 1000000
Years: 115

Answer 1

So, the code is actually running, but not producing the correct answers, correct?

Look at the code for the while loop that is supposed to calculate the number of years required:

while (start < end)
{
    start += (start / 2);
    years++;
}

It says that the population increased by 1/2 each year. Where did you get this from?

The program spec says that the population increases by 1/3 each year from births and decreases by 1/4 from deaths. That's not a net change of 1/2. Simply put, the formula that calculates annual increase is wrong. Also, don't try to simplify the formula to simply add a certain amount. It will introduce rounding/truncation errors.

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