>>584
#include <stdio.h>

int main(int argc, char *argv[]){
int i;
double n, sum=0;
for(i=1; i<argc; i++){
sscanf(argv[i],"%lf",&n);
sum += n;
}
printf("%-10.2f\n",sum/(argc-1));
return 0;
}

実行例:
./a.out 3 5.6 8.912
5.84