Question

Drivers are concerned with the mileage their automobiles get. One driver has kept track of several tankfuls of gasoline by recording the miles driven and gallons used for each tankful. Develop a C# app that will input the miles driven and gallons used (both as integers) for each tankful. The app should calculate and display the miles per gallon obtained for each tankful and display the combined miles per gallon obtained for all tankfuls up to this point. All averaging calculations should produce floating-point results. Display the results rounded to the nearest hundredth. Use the Console class’s ReadLine method and sentinel-controlled repetition to obtain the data from the user.

Write the code where the Bold comments are.

The code from Gas.cs is:

/ Exercise 5.17 Solution: Gas.cs
// Application calculates average mpg
using System;

public class Gas
{
   // perform miles per gallon calculations
   public static void Main( string[] args )
   {
      int miles; // miles for one tankful
      int gallons; // gallons for one tankful
      int totalMiles = 0; // total miles for trip
      int totalGallons = 0; // total gallons for trip

      double milesPerGallon; // miles per gallon for tankful
      double totalMilesPerGallon; // miles per gallon for trip

      // prompt user for miles and obtain the input from user

      // exit if the input is -1 otherwise, proceed with the program
      while ( miles != -1 )
      {
         // prompt user for gallons and obtain the input from user
         Console.Write( "Enter gallons: " );
         gallons = Convert.ToInt32( Console.ReadLine() );

         // add gallons and miles for this tank to totals

         // calculate miles per gallon for the current tank
         if ( gallons != 0 )
         {
            milesPerGallon = ( double ) miles / gallons;
            Console.WriteLine( "MPG this tankful: {0:F}",
               milesPerGallon );
         } // end if statement

         if ( totalGallons != 0 )
         {
                     // calculate miles per gallon for the total trip

         } // end if statement

         // prompt user for new value for miles
         Console.Write( "Enter miles (-1 to quit): " );
         miles = Convert.ToInt32( Console.ReadLine() );
      } // end while loop      
   } // end Main
} // end class Gas

Answer 1

Below is the solution:

code:

using System;

namespace GasOfMiles
{
    public class Gas
    {
        static void Main(string[] args)
        {
            int miles; // miles for one tankful
            int gallons; // gallons for one tankful
            int totalMiles = 0; // total miles for trip
            int totalGallons = 0; // total gallons for trip

            double milesPerGallon; // miles per gallon for tankful
            double totalMilesPerGallon; // miles per gallon for trip

            // prompt user for miles and obtain the input from user
            Console.Write("Enter miles (-1 to quit): ");
            miles = Convert.ToInt32(Console.ReadLine());
            // exit if the input is -1 otherwise, proceed with the program
            while (miles != -1)
            {
                // prompt user for gallons and obtain the input from user
                Console.Write("Enter gallons: ");
                gallons = Convert.ToInt32(Console.ReadLine());

                // add gallons and miles for this tank to totals
                totalMiles += miles;
                totalGallons += gallons;

                // calculate miles per gallon for the current tank
                if (gallons != 0)
                {
                    milesPerGallon = (double)miles / gallons;
                    Console.WriteLine("MPG this tankful: {0:F}",
                       milesPerGallon);
                } // end if statement

                if (totalGallons != 0)
                {
                    // calculate miles per gallon for the total trip
                    totalMilesPerGallon = (double)totalMiles / totalGallons;
                    Console.WriteLine("Total MPG: {0:F}\n", totalMilesPerGallon);

                } // end if statement

                // prompt user for new value for miles
                Console.Write("Enter miles (-1 to quit): ");
                miles = Convert.ToInt32(Console.ReadLine());
            } // end while loop
            Console.ReadKey();
        }
    }
}

sample output: