Geeting "0" solution of an equation :(

divinding int/int gives you int result

here is your code

            Console.WriteLine("Enter Year of Construction:");

            int Year = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("Enter Span of the Bridge:");

            int Span = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("Enter the Slab thickness:");

            double Thickness = Convert.ToDouble( Console.ReadLine());

            Console.WriteLine("Enter Width of the Bridge:");

            int Width = Convert.ToInt32(Console.ReadLine());

            if (Year < 1930)
            {

                double Thickness1 = (9.00 / 10.00) * Thickness;

                Console.WriteLine(Thickness1);

                Console.ReadLine();
            }

see C# specification here

http://msdn.microsoft.com/en-us/library/aa691373%28v=vs.71%29.aspx

hope it helps