Thread: Caught in a Loop

Hi,

I'm working on a program that should do the following:

Prompt a user to enter the amount of gallons used
Prompt a user to enter the amount of miles driven
Give the average miles / gallon

This program should repeat this process until the user enters -1 as the sentinal value, after which the program gives the overall miles / gallon.

I've messed the code up quite a bit, from trying to get it to work. What happens is the first prompt prints okay, but after I enter a number (12.8 in this case), the program does nothing. So if I hit enter, it prints the same line again but with the next prompt on the same line. If I hit enter again, I go into a loop. Any help is appreciated! Here's my code:

Code:

#include <stdio.h>

int main()
{
        float average1, average2, gallons;
        int counter,  miles;

        counter = 0;

        printf( "Enter the gallons used, -1 to end: " );
        scanf( "%f\n", &gallons );

        printf( "Enter the miles driven, -1 to end: ");
        scanf( "%d", &miles );

        while ( gallons != -1 ){

                printf( "Enter the gallons used, -1 to end: " );
                scanf( "%f", &gallons );
                
                printf( "Enter the miles driven, -1 to end: ");
                scanf( "%d", &miles );
        
        while ( gallons != -1 ){

                printf( "Enter the gallons used, -1 to end: " );
                scanf( "%f", &gallons );
        
                printf( "Enter the miles driven, -1 to end: ");
                scanf( "%f", &miles );
}
                if ( counter != 0 ) {
                average1 = ( float ) miles / gallons;
                printf( "The average miles / gallon is %.6f", average1 );
        }
        else
                printf( "No information was entered\n" );

  return 0;
}