C: 2 User input fields when requesting 3 - c

Question

From what I understand I should be getting 3 user input prompts, Trip Distance, Car MPG, and Gas Dollars Per Gallon to calculate total trip cost. Whenever I run the code, I only get prompted to input trip distance and car mpg, it skips gas dpg. How do I get it to recognize 3 user inputs?
int main() {
int miles;
double milesPG;
double dollarsPG;
double gasCost = (miles * (1.0 / milesPG) * dollarsPG);
printf("Input trip distance: ", miles);
scanf("%d", &miles);
printf("\nInput car miles per gallon: ", milesPG);
scanf("%0.2lf", &milesPG);
printf("\nInput gas dollars per gallon: ", dollarsPG);
scanf("%0.2lf", &dollarsPG);
printf("\nTotal trip cost is %0.2lf \n", gasCost);
return 0;
}

Answer 1

There are multiple problems in your code:
you do not include <stdio.h>
you compute gasCost before the values of miles, milesPG and dollarsPG are input. Since these variables are uninitialized, this has undefined behavior.
passing the uninitialized values to the printf() statements for prompting is useless and actually has undefined behavior as these variables are uninitialized.
the conversion format "%0.2lf" is invalid for scanf(). You cannot specify how many places to input, just the maximum number of bytes to read, which is not useful in your case.
Here is a modified version:
#include <stdio.h>
int main() {
int miles;
double milesPG;
double dollarsPG;
printf("Input trip distance: ");
if (scanf("%d", &miles) != 1)
return 1;
printf("\nInput car miles per gallon: ");
if (scanf("%lf", &milesPG) != 1)
return 1;
printf("\nInput gas dollars per gallon: ");
if (scanf("%lf", &dollarsPG) != 1)
return 1;
double gasCost = (miles * (1.0 / milesPG) * dollarsPG);
printf("\nTotal trip cost is %.2f\n", gasCost);
return 0;
}