求和、均值

            double[] scores = new double[3];//定义3个元素的空数组
            double sum = 0;
            for(int i = 0; i < scores.Length; i++)
            {
                Console.Write("请输入第" + (i + 1) + "个分数：");
                scores[i] = int.Parse (Console.ReadLine());//
                sum += scores[i];
            }
            Console.WriteLine(sum);
            Console.WriteLine(sum/scores.Length);//平均值，double型
            Console.ReadKey();