static void Main(string[] args)
{
Console.WriteLine("Enter a radius: ");
double userInput = Double.Parse(Console.ReadLine());
double area = Area.GetArea(userInput);
double diameter = Diameter.GetDiameter(userInput);
double circumference = Circumference.GetCircumference(userInput);
Console.WriteLine("Area: " + area + " Diameter: " + diameter + " Circumference: " + circumference);
Console.WriteLine("Enter your vehicle's MPG: ");
int mpg = int.Parse(Console.ReadLine());
double gasGallonsPerRotation = circumference / mpg;
Console.WriteLine("Gallons of gas that will be used to go around this circle: " + gasGallonsPerRotation);
}