What's wrong with this code? It's C and when I run it's just giving me back a ##Question_Title##.00.

Question

float monthlyPayment = 1 - pow((1 monthlyInterestRate), -numberPayments);

monthlyPayment = monthlyInterestRate / monthlyPayment;

monthlyPayment = loanAmount * monthlyPayment;

Answer 1

You are doing arithmetic division , cast everything to float or double.

Answer 2

Post all your code if you can. This snap shot you posted doesn't have enough info.

--Thanks for the code.  

I see two more mistakes.  unsigned what?

unsigned int loanAmount = 150000;

unsigned int numberPayments = loanLength * MONTHS_IN_YEAR;

A helpful hint would be to put cout statements in your code to see the values as they change.  You would spot the mistake by yourself.  Your monthlyPayment forumula is wrong.  I added the link where you can correct it.  I outputted the values as my debugger stepped through your code.

/*

* File:   YahooQuestion.cpp

* Author: Chris

*

* Created on August 13, 2008, 8:37 PM

*/

#include <stdlib.h>

//mortgage.cpp - visual c++

#include <iostream>

Thanks for the code.

#include <cmath>

int main()

{

unsigned loanAmount = 150000;

float annualInterestRate = 6.0;

unsigned short loanLength = 30;

const unsigned short MONTHS_IN_YEAR = 12;

float monthlyInterestRate = annualInterestRate / MONTHS_IN_YEAR;

//monthlyInterestRate is .5

monthlyInterestRate = monthlyInterestRate/100;

//monthlyInterestRate is 0.00499999989

unsigned numberPayments = loanLength * MONTHS_IN_YEAR;

//numberPayment is 360

float monthlyPayment = 1 - pow((1 + monthlyInterestRate), -numberPayments);

//negative Infinity...This jumps out as wrong.  I added the //correct forumla below.

monthlyPayment = monthlyInterestRate/monthlyPayment;

//monthlyPayment is -0 because of the earlier neg infinity.

monthlyPayment = loanAmount * monthlyPayment;

//monthlyPayment is -0  because of neg infinity.

std::cout << "Assuming a loan in the amount of $" << loanAmount << ", at " << annualInterestRate << "% interest, over " << loanLength << " years, the monthly payment would be $";

std::cout << monthlyPayment << ".\n\n";

std::cout.setf(std::ios_base::fixed);

std::cout.setf(std::ios_base::showpoin...

std::cout.precision(2);

http://www.hughchou.org/calc/formula.htm...

Okay now for the big monthly payment (M) formula, it is:

         M  =  P  x (J/ (1  - ( 1 + J ) ^ -N)

                

                      

First you must define some variables to make it easier to set up:

P = principal, the initial amount of the loan

I = the annual interest rate (from 1 to 100 percent)

L = length, the length (in years) of the loan, or at least the length over which the loan is amortized.

The following assumes a typical conventional loan where the interest is compounded monthly. First I will define two more variables to make the calculations easier:

J = monthly interest in decimal form = I / (12 x 100)

N = number of months over which loan is amortized = L x 12