2 D配列(平均値を求める)2 Dはいれつ

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(" {0}      : ",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}\t", a[i, j]);
                }
                num[i] = (double)sum[i] / a.GetLength(1);
                Console.WriteLine("   ：{0}", num[i]);
                Console.WriteLine("
");
            }
        }
    }
}

2 D配列(平均値を求める)2 Dはいれつ 
1.10人の学生の5項目の成績をランダムに発生し、平均値を求める

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(" {0} ：", 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("\t");
                    sum[i] += a[i][j];
                }
                for (int n = 1; n <= temp - a[i].Length; n ++ )
                {
                    Console.Write("\t");
                }
                num = (double)sum[i] / a[i].Length;
                Console.Write("   ：{0:f2}",num);
                Console.WriteLine();
            }
        }
    }
}

インタリーブ配列
ランダムに5行の乱数を生成し、行ごとに平均値を算出する