这是个求1-100奇数之和的平均值的程序
# include <stdio.h>

int main(void)
{
    int i;
    float pj, sum1, sum;
    sum = 0;
    sum1 = 0;
    for (i=1; 1<=100; ++i)
    {
        if (i%2 != 0)
        {
            sum = sum + i;
            sum1 = sum1 + 1;
        }
    }
    pj = sum/sum1;

    printf("平均值为：%f\n", pj);

    return 0;
}

你的错误太多了吧。。。。

明天给你写上

# include <stdio.h>

 
int main(void)

 {
     int i;
     float pj, sum1, sum;
     sum = 0;
     sum1 = 0;
     for (i=1; 1<=100; ++i)
     {
         if (i%2 != 0)
         {
             sum = sum + i;
             sum1 ++;//这个才是统计奇数个数的，你原来那个是求奇数和的，和上式相同
         }
     }
     pj = sum/sum1;

 
    printf("平均值为：%f\n", pj);

 
    return 0;

 } 

float a=0,i,j=0;
for(i=0;i<100;i++)
if((int)i%2==1)
{a=a+i;j++;}
printf("%.2f",a/j);

楼主就错了一个地方，for (i=1; i<=100; ++i)写成for (i=1; 1<=100; ++i)

# include <stdio.h>

int main(void)
{
    int i,sum1;
    float pj, sum;
    sum = 0;
    sum1 = 0;
    for (i=1; 1<=100; i++ )
    {
        if (i%2 != 0)
        {
            sum = sum + i;
            sum1++;
        }
    }
    pj = sum/sum1;

    printf("平均值为：%f\n", pj);

    return 0;
}

# include <stdio.h>

int main(void)
{
    int i;
    float pj, sum1, sum;
    sum = 0;
    sum1 = 0;
    for (i=1; 1<=100; ++i)//此处1<=100会造成for循环无法终止，楼主把1改成i就可以了
    {
        if (i%2 != 0)
        {
            sum = sum + i;
            sum1 = sum1 + 1;
        }
    }
    pj = sum/sum1;

    printf("平均值为：%f\n", pj);

    return 0;
}

程序编译执行后的输出是50.000000

# include <stdio.h>

int main(void)
{
    int i;
    float pj, sum1, sum;
    sum = 0;
    sum1 = 0;
    for (i=1; 1<=100; ++i)//此处1<=100会造成for循环无法终止，楼主把1改成i就可以了
    {
        if (i%2 != 0)
        {
            sum = sum + i;
            sum1 = sum1 + 1;
        }
    }
    pj = sum/sum1;

    printf("平均值为：%f\n", pj);

    return 0;
}

程序编译执行后的输出是50.000000

#include <stdio.h>

int main (void) {

        int i=1,sum=0;

        while(i<100) {
                sum+=i;
                i+=2;
        }
        printf("sum=%i,average=%.2f\n",sum,(float)sum/50);
        return 0;

}