using System;

​

namespace Csharp

{

    class Csharp

    {

        public static void Main()

        {

​

            double r, chu_vi, dien_tich;

            double PI = 3.14;

            Console.Write("Nhap ban kinh duong tron: ");

            r = Convert.ToDouble(Console.ReadLine());

            chu_vi = 2 * PI * r;

            Console.WriteLine("\nChu vi duong tron la: {0}", chu_vi);

            dien_tich = PI * r * r;

            Console.WriteLine("Dien tich duong tron la: {0}", dien_tich);

            Console.Read();  

​

            Console.ReadKey();

        } 

    }

}

​

​