Miscellany

// gallons.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "iostream"

double miles_per_gallon(double litres, double miles);

const double LITRES_PER_GALLON = (1 / 0.264179);

int _tmain(int argc, _TCHAR* argv[])
{
	using namespace std;

	double litres, miles, miles_per_gallon;

	cout << "How many litres of petrol did your car use? ";
	cin >> litres;
	cout << "How many miles did you go? ";
	cin >> miles;

	miles_per_gallon = miles_per_gallon(litres, miles);

	cout << "Your car goes " << miles_per_gallon << " miles per gallon";
	return 0;
}

double miles_per_gallon(double litres, double miles)
{
	double miles_per_litre = miles/litres;

    miles_per_gallon = miles_per_litre * LITRES_PER_GALLON;
	return (miles_per_gallon);
}