#include <stdio.h>
#include <math.h>

int i, problem = 0;
float readings[6];
float average, average10, average15, diff;

void checkwithin10pc()
{
   for(i = 0; i < 6; i++)
   {
      diff = fabs(readings[i] - average);
      if (diff > average10)
      {
         problem++;
         if(problem == 1) printf("\nThe following problems occurred:\n");
         printf("%d. Voltage at hour %d was %.1f volts (difference of %.1f volts).\n", problem, i + 1, readings[i], diff);
      }
   }
}

void checkwithin15pc()
{
   for(i = 1; i < 6; i++)
   {
      diff = fabs(readings[i] - readings[i - 1]);
      if (diff > average15)
      {
         problem++;
         if(problem == 1) printf("\nThe following problems occurred:\n");
         printf("%d. Voltage change from hour %d to hour %d was %.1f volts.\n", problem, i, i + 1, diff);
      }
   }
}


int main()
{
   float total = 0.0f;

   /* simulate obtaining 6 readings by asking user to input them */

   for(i = 1; i <= 6; i++)
   {
       printf("Enter reading at hour %d to 1 dp : ", i);
       scanf("%f", &readings[i - 1]);
       if (readings[i - 1] < 0)
       {
         printf("Can't be negative, please re-enter.\n");
         i--;
       }
       else
       {
          total += readings[i - 1];
       }
   }

   average = total / 6.0f;
   average10 = .1f * average;
   average15 = .15 * average;

   printf("\nThe average is %.1f volts.\n", average);
   printf("10%% = %.1f volts.\n", average10);
   printf("15%% = %.1f volts.\n", average15);

   checkwithin10pc();
   checkwithin15pc();

   if(!problem) printf("No problems were encountered.");
   return 0;
}