二维数组（求平均值）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace twoArray
{
    class Program
    {
        static void Main(string[] args)
        {
            int [,]a = new int[10,5];
            Random ran = new Random();
            int[] sum = new int[10];
            double[] num = new double[10];
            for (int i = 0; i < a.GetLength(0); i++)
            {
                Console.Write("第{0}个学生的成绩: ",i+1);
                for (int j = 0; j < a.GetLength(1); j++)
                {
                    a[i , j] = ran.Next(100);
                    sum[i] += a[i , j];
                    Console.Write(" {0}	", a[i, j]);
                }
                num[i] = (double)sum[i] / a.GetLength(1);
                Console.WriteLine("平均值：{0}", num[i]);
                Console.WriteLine("
");
            }
        }
    }
}

二维数组（求平均值） 

1.随机产生10个学生的5项成绩并求出平均值

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace staggerArray
{
    class Program
    {
        static void Main(string[] args)
        {
            int [][] a=new int[5][]; 
            Random ran = new Random();
            int[] sum = new int[a.Length];
            double num = 0;
            int i , temp=0;
            for ( i = 0; i < a.Length;i++ )
            {
               a[i] = new int[ran.Next(5)+1];
                if(temp < a[i].Length){
                    temp = a[i].Length;
                }
            } 
            for (i = 0; i < a.Length; i++)
            {
                Console.Write("第{0}行：", i + 1);
                for(int j = 0;j < a[i].Length;j++){
                    a[i][j] = ran.Next(100)+1;
                    Console.Write(a[i][j]);
                    Console.Write("	");
                    sum[i] += a[i][j];
                }
                for (int n = 1; n <= temp - a[i].Length; n ++ )
                {
                    Console.Write("	");
                }
                num = (double)sum[i] / a[i].Length;
                Console.Write("平均值：{0:f2}",num);
                Console.WriteLine();
            }
        }
    }
}

交错数组（求平均数）

随机产生5行随机数，并每行都算出平均值