Question

Write a C program that calculates exact change. In order to receive full credit, please remember that only int arithmetic is exact, so you’ll need to break up your double into two ints, the one before the decimal point and the one after the decimal point. Another point worth mentioning is that the % operator gives the remainder. In other words, when working with int values, 9 / 5 = 1 whereas 9 % 5 = 4. Keep this in mind when you see the sample values shown below.

I have this program and it works for all the examples but when I inter sale price of 25.01 and total payment of $50; the curect answer for this example is 24 dollars, 3 quarters, 2 dimes, 0 nickels and 4 pennies but the code that I have gives me this answer

24 dollars, 3 quarters, 2 dimes, 0 nickels and 3 pennies

Please check my program hopefully we can fix it .

#include <stdio.h>
#include <stdlib.h>

int main() {
  
//Declare variables
float userNUmber;
int change, quarters, dimes, nickels, pennies;

//Prompt and read the amount as an input from the user
//printf("Enter the sales price: ");
float sales;
scanf("%f",&sales);
//printf("Enter the cash paid: ");
float cash;
scanf("%f",&cash);
userNUmber=cash-sales;
//printf("Here's your change: %.2f\n",userNUmber);
//for Calculate the number of quarters

//this part is to Convert float to int data type for change variable
int dollars=userNUmber;
userNUmber=userNUmber-(float)dollars;
change = (userNUmber*100);
quarters = change / 25;

// Calculate remaining change needed
change = change % 25;

//to Calculate the number of dimes
dimes = change / 10;

// to Calculate remaining change needed
change = change % 10;

//to Calculate the number of nickels
nickels = change / 5;

// part for Calculate pennies
change = change%100;
pennies = change %5;

//int penn
//pennies = penn;
//penn = change%5;

//for Display the amount of coins in quarters, dime, nickle and pennies
printf("%d dollars, %d quarters, %d dimes, %d nickels and %d pennies\n",dollars,quarters,dimes,nickels,pennies);

return (0);
}

Answer 1

#include <stdio.h>
#include <stdlib.h>
int main() {
//Declare variables
double userNUmber;
int change, quarters, dimes, nickels, pennies;
//Prompt and read the amount as an input from the user
//printf("Enter the sales price: ");
float sales;
scanf("%f",&sales);
//printf("Enter the cash paid: ");
float cash;
scanf("%f",&cash);
userNUmber=cash-sales;
//printf("Here's your change: %.2f\n",userNUmber);
//for Calculate the number of quarters

//this part is to Convert float to int data type for change variable
int dollars=userNUmber;
userNUmber=userNUmber-(float)dollars;
userNUmber = round(userNUmber *100);
change = userNUmber;
quarters = change / 25;

// Calculate remaining change needed
change = change % 25;

//to Calculate the number of dimes
dimes = change / 10;

// to Calculate remaining change needed
change = change % 10;
//to Calculate the number of nickels
nickels = change / 5;
////// part for Calculate pennies
change = change%100;
pennies = change %5;

//////for Display the amount of coins in quarters, dime, nickle and pennies
printf("%d dollars, %d quarters, %d dimes, %d nickels and %d pennies\n",dollars,quarters,dimes,nickels,pennies);
return (0);
}

OUTPUT :

when you were getting the userNUmber as it is float while subtracting userNUmber from dollar it 98.987 due to floating point precision and while you were converting that directly to int . so change change became 98 instead of 99 what it should be .

So, before assigning userNUmber to change we should do:

userNUmber = round(userNUmber *100);

and then assign it to change after rounding-off.
change = userNUmber;