Problem with current project

[layzer]

I am having trouble getting this to work. I cannot figure out if its a syntax error or what.
Here is the original problem:


Payment = Rate * (1 + Rate)^N / ((1+Rate)^N -1) * Loan

Rate is the monthly interest rate. Rates for loans are
expressed as annual percentage rate (e.g., 18.0% APR).
N is the number of payments.
Loan is the amount of the loan.

Write a program with an interactive console dialog to
accept input from the keyboard. Then calculate the
monthly payment, amount paid back, and the interest paid.
Display a formatted report similar to:

Loan Amount: $ 10000.00
Annual Interest Rate: 12.00%
Number of Payments: 36
Monthly Payment: $ 332.14
Amount Paid Back: $ 11957.15
Interest Paid: $ 1957.15


Here is my code so far.

  #include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <stdlib.h>

using namespace std;

int main()
{
    //define variables
    
    double loanamount;
    
    double rate;
    
    double payments;
   
    double monthly;
    
    double payback;
    
    double intrest;
    
    double a;
    
    double b;
    
    double c;
    
    //inputs
    cout<<"Enter Loan Amount: ";
    cin>>loanamount;
    
    
    cout<<"Enter Intrest Rate: ";
    cin>>rate;
    
    cout<<"Enter Number of Payments: ";
    cin>>payments;
    
    system("CLS");
   
    
    //define formula 
    a = rate * (pow((1+rate),payments));
    b = (pow((1+rate),(payments-1)*loanamount));
    monthly = a/b;
    //formula
    
    
   
    //outputs
    cout<<"Loan Amount: "<<loanamount<<endl;
    cout<<"Anual Intrest Rate: "<<rate<<endl;
    cout<<"Number Of payments: "<<payments<<endl;
    cout<<"Monthly Payment: "<<monthly<<endl;
    cout<<a<<endl;
    cout<<b<<endl;
    cout<<c;
    
    
            
    
    
    
    return 0;
}

The reason there are cout's for A,B,C is just for testing trying to get the numbers to come out right. So far i cannot figure out how to get the pow() function to work correctly. Any help is appreciated! Thanks!

[28poGNh0]

This line (pow((1+rate),(payments-1)*loanamount)); it is not as is shown in the formula

((1+Rate)^N -1) * Loan

maybe you need to turn it to (pow((1+rate),payments)-1)*loanamount;

also you have a lot of unused variables check them

#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <stdlib.h>

using namespace std;

int main()
{
    //define variables

    double loanamount;
    double rate;
    double payments;
    double monthly;
    double a;
    double b;

    //inputs
    cout<<"Enter Loan Amount: ";
    cin>>loanamount;

    cout<<"Enter Intrest Rate: ";
    cin>>rate;

    cout<<"Enter Number of Payments: ";
    cin>>payments;

    system("CLS");

    //define formula    Payment = Rate * (1 + Rate)^N / ((1+Rate)^N -1) * Loan
    a = rate * (pow((1+rate),payments));
    b = (pow((1+rate),payments)-1)*loanamount;
    monthly = a/b;
    //formula

    //outputs
    cout<<"Loan Amount: "<<loanamount<<endl;
    cout<<"Anual Intrest Rate: "<<rate<<endl;
    cout<<"Number Of payments: "<<payments<<endl;
    cout<<"Monthly Payment: "<<monthly<<endl;
    cout<<a<<endl;
    cout<<b<<endl;

    return 0;
}

Hope that helps

[layzer]

The numbers pushed out still do not match the example display given.
Putting 10000 as loan amount.
.12 as intrest rate.
and 36 as monthly payments.

The output is a wacky scientific notation answer?

[28poGNh0]

Thats because you declared those variables as doubles
what are you expecting as number?

[layzer]

It should come out as 332.14 for monthly payments, Not 1.3454E^-64 or whatever.

[28poGNh0]

based on this formula the numbers obtained will be a huge one beleive me

the scientific form for double occurs when the value riches a big number I guess 999999 ,just to simplify

If you want a double value without a scientific notation in this exp turn this lines

cout<<a<<endl;
cout<<b<<endl;

cout<< fixed << a << endl;
cout<< fixed << b << endl;

[layzer]

#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <stdlib.h>

using namespace std;

int main()
{
    //define variables

    double loanamount;
    double rate;
    double payments;
    double monthly;
    double a;
    double b;
    double c;
    
    //inputs
    cout<<"Enter Loan Amount: ";
    cin>>loanamount;

    cout<<"Enter Intrest Rate: ";
    cin>>rate;

    cout<<"Enter Number of Payments: ";
    cin>>payments;

    system("cls");

    //define formula    Payment = Rate * (1 + Rate)^N / ((1+Rate)^N -1) * Loan
    a = pow((1+rate),payments);
    b = pow((1+rate),payments-1);
    c = rate * a/b *loanamount;
    //monthly = (rate * ((pow(1+rate, payments)))/(pow(rate,payments-1)))*loanamount;
    
    //formula

    //outputs
    cout<<"Loan Amount: "<<loanamount<<endl;
    cout<<"Anual Intrest Rate: "<<rate<<endl;
    cout<<"Number Of payments: "<<payments<<endl;
    cout<<"Monthly Payment: "<<fixed<<c<<endl;
  

    return 0;

This is what i have so far and this is my output

Enter Loan Amount: 10000
Enter Intrest Rate: .12
Enter Number of Payments: 36
sh: cls: command not found
Loan Amount: 10000
Anual Intrest Rate: 0.12
Number Of payments: 36
Monthly Payment: 1344.000000


Thats still not right. I know i can put in a setprecision(2) to get rid of all those zero's but still all around wrong number.

[Josue Molina]

Damn it, this thread is driving me crazy; it keeps popping up in the forum. Here you go, at last:

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main()
{
    double c, r, n;

    cout << "Enter Loan Amount: ";
    cin >> c;

    cout << "Enter Intrest Rate: ";
    cin >> r;
    r /= 1200;

    cout << "Enter Number of Payments: ";
    cin >> n;
    
    double m = (c * r * pow(1 + r, n)) / (pow(1 + r, n) - 1);
    
    cout << fixed << setprecision(2) << "Loan Amount: $" << c << endl;
    cout << fixed << setprecision(2) << "Annual Interest Rate: " << r * 1200 << '%' << endl;
    cout << fixed << "Number of Payments: " << n << endl;
    cout << fixed << setprecision(2) << "Monthly Payment: $" << m << endl;
    cout << fixed << setprecision(2) << "Amount Paid Back: $" << m * n << endl;
    cout << fixed << setprecision(2) << "Interest Paid: $" << m * n - c << endl;
    
    return 0;
}

Inputting 10000, 12 and 36 yields your desired result.

Go away!