What am I doing wrong with for loop? - c

Question

Please help. I am supposed to Calculate 3 MPG for 3 tanks. I am able to do it without using a loop. However, I am supposed to use a for-loop to replace one section of code. I think I have the proper code but I just don't know if I placing it correctly.
So, instead of writing "Enter the number of miles driven", 3 times, it's supposed to be replaced by for (miles = 1; miles <=3; miles = miles+1) {
miles = miles + 0;. IS this right? I asked my professor do we use counters, or nested loops, and I was told no. What am I doing wrong?
#include <stdio.h>
int main (void)
{
/*Variable Delclarations*/
/*----------------------*/
float gallons = 0;
float miles = 0;
float mpg = 0;
float avg = 0;
printf ("\nEnter the number of gallons used in tank #1: ");
scanf ("%f/n", &gallons);
for (miles = 1; miles <=3; miles = miles+1) {
miles = miles + 0;
printf ("Enter the number of miles driven: ");
}
scanf ("%f/n", &miles);
printf ("/nThe miles per gallon for this tank is: %.1f\n miles per gallon",
(float)miles/gallons);
printf("\n\n"); /* new line */
printf ("Enter the number of gallons used in tank #2: ");
scanf ("%f/n", &gallons);
for (miles = 1; miles <=3; miles = miles+1)
miles = miles + 0;
printf ("Enter the number of miles driven: ");
scanf ("%f/n", &miles);
printf ("The miles per gallon for this tank is: %.1f\n", (float)miles/gallons);
printf("\n\n"); /* new line */
printf ("/nEnter the number of gallons used in tank #3: ");
scanf ("%f/n", &gallons);
for (miles = 1; miles <=3; miles = miles+1)
miles = miles + 0;
printf ("Enter the number of miles driven: ");
scanf ("%f/n", &miles);
printf ("The miles per gallon for this tank is: %.1f\n", (float)miles/gallons);
printf("\n\n"); /* new line */
printf ("Your overall average miles per gallon for three tanks is %.1f\n")
scanf ("%f/n", &avg);
}

Answer 1

So in this case there is no need for three separate loops, everything can be handled in one. What you're trying to do in this exercise is get three separate inputs for your tanks. these inputs can be gathered using the scanf command. For each loop your gallons and miles variable should be assigned to a value of 0;
this would result in the following code for the inside of the loop:
miles = 0;
gallons = 0;
printf ("Enter the number of gallons used in tank #%i: ", tank);
scanf ("%f", &gallons);
printf ("Enter the number of miles driven: ");
scanf ("%f", &miles);
printf ("The miles per gallon for this tank is: %.1f miles per gallon", (float)(miles / gallons));
avg += (miles / gallons);
printf("\n\n");
you can add the result of miles / gallons onto average and at the end divide this by the total amount of tanks.
If you do all of this you should end up with something that looks like this:
#include <stdio.h>
int main (void)
{
float gallons = 0;
float miles = 0;
float avg = 0;
int tank_amount = 3;
for (int tank = 1; tank <= tank_amount; tank++) {
miles = 0;
gallons = 0;
printf ("Enter the number of gallons used in tank #%i: ", tank);
scanf ("%f", &gallons);
printf ("Enter the number of miles driven: ");
scanf ("%f", &miles);
printf ("The miles per gallon for this tank is: %.1f miles per gallon", (float)(miles / gallons));
avg += (miles / gallons);
printf("\n\n");
}
printf ("Your overall average miles per gallon for three tanks is %.1f\n", (avg / tank_amount));
}
Also be sure to indent your code in a nice and readable way and use {} brackets for your loops, this makes it a lot easier to read, which also helps if u need to debug it :)

Answer 2

You have three for() loops. The first one contains two statements: a print statement that will therefore be printed three times, and "miles = miles + 0", which does exactly nothing. The other two for loops (since they don't have braces) include only one statement, the same "miles = miles + 0", which does nothing.
Always use braces with your loops, and make sure that whatever you want to happen multiple times is inside the braces. And indent your code so that you can see at a glance what's inside and outside. Finally, if you use a variable like "miles" in the for() statement, don't also modify it inside the loop.