### Monthly Payment

 ``123456789101112131415161718192021222324252627282930313233343536373839`` ``````// Reaper #include #include using namespace std; int main() { float L , monthly , interest , amount , annual , monthlyrate; int n; cout << "This is a monthly payments program.\n\n"; cout << "Enter the loan amount: \$"; cin >> L; cout << "Enter the rate percent in decimal form: "; cin >> annual; cout << "Enter the number of payments: "; cin >> n; cout.setf(ios_base::fixed , ios_base::floatfield); cout.precision(2); monthly = (L * pow(monthlyrate + 1, n) * monthlyrate) / (pow(monthlyrate + 1, n) - 1); amount = monthly * n; monthlyrate = annual / 12; interest= monthlyrate * n; cout << "\n\n"; cout << "Loan Amount: \$" << L << endl; cout << "Monthly Interest Rate: " << monthlyrate << "%" << endl; cout << "Number Of Payments: " << n << endl; cout << "Monthly Payment: \$" << monthly << endl; cout << "Amount Paid Back: \$" << amount << endl; cout << "Interest Paid: \$" << interest << endl; return 0; }``````

Im having trouble with line 24, when i run my program for monthly payment and amount paid back i get -nan.

I know my line 24 is wrong somewhere but i dont know where, heres the formula , anyone see whats wrong.

Payment = rate * (1 + rate)^n / (1 + rate)^n * L i think this is correct.
You haven't initialised monthlyrate.

Initialisation is the of the main sources of error in programming, so always be aware of it.

I tend to declare my variables 1 per line, initialise them to something (as long as this doesn't cause problems later), and put a comment to say what the variable means.

HTH

Edit: You probably need to calculate what the monthly rate is.
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"Run-Time Check Failure #3 - The variable 'monthlyrate' is being used without being initialized." - VS2012

I initialized it like the guy said from above, float L; float monthly; float interest; and the program still crashed.

Then I set default values because if you don't, it'll grab whatever memory was left in the RAM and use it.

Since you're passing monthlyrate to a function before it ever has a value, it crashes. (pow(x, y) is a function)

So the initialization you used would have been fine, if you had just set some default values, I think. Just to be safe, it'd be good programming practice to declare your variables line - by - line and set default values for each one.

example:
float L = 0;
float monthly = 0;
float monthlyrate = 0; etc...etc...
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ok i will ,and what about my interest, my interest = monthlyrate * n, but that has to be wrong because its not showing up the right answer.

and by the way my monthlyrate works now.

if i enter

10000 for l
.12 for annual
36 for n

my loan to amount paid back is correct my interest is suppose to be 1957.16 but i get 0.36 what else am i suppose to have in interest.

codiddle wrote:
 I initialized it like the guy said from above, float L; float monthly; float interest; and the program still crashed.

That is declaration, not initialisation. Initialisation means assigning a value, which you are calling a default value.

Default value has a special meaning in C++, namely in assigning a value to a parameter of a function, which means that the user does not have to supply an argument in the function call, unless they want a value different to the default value.

@Reaper1

As I said above you need to calculate the value of monthlyrate, before you use it on line 24.
I did initialize it and it works for me, the only part that wrong it the interest part. If i enter the the numbers i wrote above interest should show 1957.16 , but i get 0.36 everytime, i know im missing something in interest calculation but i dont know what heres my updated code.

 ``123456789101112131415161718192021222324252627282930313233343536373839`` ``````// Reaper #include #include using namespace std; int main() { float L , monthly , interest , amount , annual , monthlyrate; int n; cout << "This is a monthly payments program.\n\n"; cout << "Enter the loan amount: \$"; cin >> L; cout << "Enter the rate percent in decimal form: "; cin >> annual; cout << "Enter the number of payments: "; cin >> n; cout.setf(ios_base::fixed , ios_base::floatfield); cout.precision(2); monthlyrate = annual / 12; monthly = (L * pow(monthlyrate + 1, n) * monthlyrate) / (pow(monthlyrate + 1, n) - 1); amount = monthly * n; interest= monthlyrate * n; cout << "\n\n"; cout << "Loan Amount: \$" << L << endl; cout << "Monthly Interest Rate: " << monthlyrate << "%" << endl; cout << "Number Of Payments: " << n << endl; cout << "Monthly Payment: \$" << monthly << endl; cout << "Amount Paid Back: \$" << amount << endl; cout << "Interest Paid: \$" << interest << endl; return 0; }``````

my problem now is line 27 the output is wrong.

 ``123456789101112131415161718192021222324252627282930313233343536373839`` ``````// Reaper #include #include using namespace std; int main() { float L , monthly , interest , amount , annual , monthlyrate; int n; cout << "This is a monthly payments program.\n\n"; cout << "Enter the loan amount: \$"; // enter 10,000 here cin >> L; cout << "Enter the rate percent in decimal form: "; // you enter .12 here cin >> annual; cout << "Enter the number of payments: "; // 36 here cin >> n; cout.setf(ios_base::fixed , ios_base::floatfield); cout.precision(2); monthlyrate = annual / 12; // Monthlyrate = .12/12 (.1) monthly = (L * pow(monthlyrate + 1, n) * monthlyrate) / (pow(monthlyrate + 1, n) - 1); amount = monthly * n; interest= monthlyrate * n; // interest = .1 * 36 (.36) cout << "\n\n"; cout << "Loan Amount: \$" << L << endl; cout << "Monthly Interest Rate: " << monthlyrate << "%" << endl; cout << "Number Of Payments: " << n << endl; cout << "Monthly Payment: \$" << monthly << endl; cout << "Amount Paid Back: \$" << amount << endl; cout << "Interest Paid: \$" << interest << endl; return 0; }``````
Ok i will , how can i get the right answer in the interest line 27, its outputting the wrong number. i know why it is, im just having trouble figuring out what the right equation would be.
Before i do that, im trying to wrap my mind around how you concluded that your interest should be 1957.16 in total
ok ill post the problem dont worry im not in school, im teaching myself c++ , c# , java, perl , ruby , assembly , and pretty much every other language.

heres the problem and the input for the problem and what it should look like.

18. Monthly Payments
The monthly payment on a loan may be calculated by the following formula:

monthly = (L * pow(monthlyrate + 1, n) * monthlyrate) / (pow(monthlyrate + 1, n) - 1);

Rate is the monthly interest rate, which is the annual interest rate divided by 12. (A 12
percent annual interest would be 1 percent monthly interest.) N is the number of payments
and L is the amount of the loan. Write a program that asks for these values and displays
a report similar to the following:

Loan Amount: \$10000.00
Monthly Interest Rate: 1%
Number of Payments: 36
Monthly Payment: 332.14
Amount Paid Back: \$11957.15
Interest Paid: \$1957.15

everything up to the interest is correct in my program but i cant get the interest to show 1957.15
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Anyone got any ideas?