Simple line graph snippit in C

Here's a bit of code to display distributation of grades in form of percentages and a crude line graph. If anyone sees a problem or perhaps has a question, please let me know.

Code:

/* simple graph for student averages */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void) {

   int i, j,
       student_avgs[] = { 90, 92, 88, 75, 40,
                          79, 84, 83, 91, 88,
                          88, 65, 72, 77, 90,
                          83, 85, 76, 68, 81,
                          96, 59, 64, 79, 88 },
	   /* one class student averages */

       arr_count = sizeof(student_avgs) / sizeof(student_avgs[0]), 
	   /* number of students in one class */       

       ranges[10] = { 0 };
	   /* temp array to hold distribution of averages */
	   
   for(i=0; i < arr_count; ++i) /* compute range for each student in class */
      student_avgs[i] >= 90 ? ranges[9]++ :
	  student_avgs[i] >= 80 ? ranges[8]++ :
	  student_avgs[i] >= 70 ? ranges[7]++ :
	  student_avgs[i] >= 60 ? ranges[6]++ :
	  student_avgs[i] >= 50 ? ranges[5]++ :
	  student_avgs[i] >= 40 ? ranges[4]++ :
	  student_avgs[i] >= 30 ? ranges[3]++ :
	  student_avgs[i] >= 20 ? ranges[2]++ :
	  student_avgs[i] >= 10 ? ranges[1]++ : ranges[0]++;

   puts("distribution of average grades\n==============================\n");
   
   for(i = (sizeof(ranges) / sizeof(ranges[0])) - 1; i >= 0; --i) {
      
      printf("%2d - %3d: (%2d students %2.0f%% ) ", 
	     i * 10, (i + 1) * 10, 
		 ranges[i], 
		 ranges[i] / (float)arr_count * 100); /* per of students in each range 
		                                         integer div requires cast (float) */
	  for(j=0; j < ranges[i]; ++j)
	     putchar('#'); /* output one # for each student in range */

      putchar('\n');
   } 
   
   printf("\n%d students in class\n", arr_count);
   getchar();

   return 0;
}