Please help! short while loop tracking problem.

Hello all,

I have always had problems with loop tracking problems, I seem to understand how the loop runs and when it ends and the general idea of how it works. However, when I take a programming test and I need to track the output of a short loop, I fail most of the time. Can someone please help me? or give me some strategy tips?

The problem below is an example, I need to find the output of SUM without a computer, just using logic and a pencil and paper.

This is what I got for my i, and sum;

__i__

0

3

9

12

__sum:__

0

3

6

9

12

So in my attempt: sum= 12 but the correct answer is sum=30.

Code:

`int main () {`

int sum=0, i=0;

while (i <=12) {

**sum = sum +i;** // before this read sum=sum+1 which was a typo:/

i= i+3;

}

printf("%d", sum);