Looping Help

[zipfur]

Im trying to build this simple program that computes the amount
of time it takes to pay off a credit card debt.

I have the user input:
balance, interest_rate(monthly), & payment(monthly)

The formula I came up with was:
balance = balance - (payment - (balance * interest_rate));

So lets say for example:
Balance = $1500
Monthly Payment = $42
Monthly Interest Rate = .015

With the above inputs, and the equation above you would get an answer of $1480.50. Because you would be paying off $19.50 the first month. How could i create a loop that would continue this formula with each new monthly balance, until it reached a balance of $0 and how could i have it print out how many months it took to pay off this debt?

I also tried a variation of the formula below to find the number of monthly payments:
N = –log(1–iA/P) / log(1+i)
N = number of payments
I = interest rate
A = balance
P = payment
But it did not work very well, does C programming compute Logrithims (LOG, LN?)

Any tips would be appreciated! Thanks...

[ygfperson]

Originally posted by zipfur


does C programming compute Logrithims (LOG, LN?)

Any tips would be appreciated! Thanks...

yes, look into math.h.

[Shadow]

This isn't the best code as it was thrown together fast, but it should do the job.

#include <stdio.h>

int main ( void )
{
	float Bill;
	float Monthly;
	float Interest;
	int MonthCount = 0;
	int Time;
	
	printf("Enter the amount of your total bill:\n");
	scanf("%f", &Bill);

	printf("Enter the monthly payments you are making:\n");
	scanf("%f", &Monthly);

	printf("Enter the interest rate you are being charged:\n");
	scanf("%f", &Interest);

	while ( Bill >= 0 )
	{
		Bill = Bill-(Monthly * (Interest/100) + Monthly);
		MonthCount++;
	}
	Time = MonthCount/12;
	printf("\n\nIt will take you %d months to pay off this debt.\n", MonthCount);
	printf("It will take you %d years to pay off this debt.", Time);
	return 0;
}

[zipfur]

Shadow thanks for the post, i appreciate your time!!! I was having trouble with that while loop - but this should set me straight -thanks...