Error outputting quotient of array and integer

Question

Code simulates the rolling of two die 36000 times and outputs "Sum = _; Frequency = _; Percentage = _". Compiled code outputs everything correctly except percentage. "Percentage = 0" when it should output the quotient of "(frequency[calcCount] /36000) * 100" Is this a conflict in data type? How can I properly output the quotient?

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SUM_SIZE 36000
#define FREQUENCY_SIZE 13

int main(void){
    int rollCount; // counter to loop through 36000 rolls of dice & sums
    int calcCount; //counter to loop through frequencies 1-12 of sum calculation

//initialize frequency counters to 0
int frequency[FREQUENCY_SIZE] = {0};

//calculation array
int calculation[SUM_SIZE];

//seed
srand((unsigned)(time(NULL)));

for (rollCount = 1; rollCount <= SUM_SIZE; rollCount++){
    //rolling first die
    int face1 = (1 + ( rand() % 6));
    //rolling second die
    int face2 = (1 + ( rand() % 6));
    int sum = face1 + face2;
    //initializing array elements
    calculation[rollCount] = sum;
    //for each roll, select value of an element of array calculation
    //and use that value as subscript in array frequency to determine
    //element to increment (which in this case is the sum frequency)
    ++frequency[calculation[rollCount]];
}

//displaying results
for (calcCount = 2; calcCount < FREQUENCY_SIZE; calcCount++){
    //calculating percentage
    int percentage = (frequency[calcCount] /36000) * 100;
    printf("Sum = %d; Frequency = %d; Percentage = %d \n", calcCount, frequency[calcCount], percentage);
}

}

Answer 1

When you do a division between two integers, the result will also be an integer and the "exact" result is truncated to fit an integer. Examples:

3/2 -> 1
10/3 -> 3
5/10 -> 0

and when you do

int percentage = (frequency[calcCount] /36000) * 100;

the part frequency[calcCount] /36000 is calculated first. It is a division between two int and it will give the result zero because frequency[calcCount] is less than 36000. Consequently multiplying with 100 still gives zero.

Instead do the multiplication first - like:

int percentage = (100 * frequency[calcCount]) /36000;

Another alternative is to use floating point like:

double percentage = (frequency[calcCount] /36000.0) * 100;
                                                ^^^
                               Notice the .0 to make 36000 a double

but then you need to change the print to use %f

double percentage = (frequency[calcCount] / 36000.0) * 100;
printf("Sum = %d; Frequency = %d; Percentage = %.2f \n", calcCount, frequency[calcCount], percentage);
                                                ^^^
                                        Notice this to print the double