Thread: Interest program

  1. #1
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    Interest program

    Can someone please help me? Okay if a principal amount is P, for which the interest is compounded Q times per year, is placed in a savings account, then the amount of money in the account (the balance) after N years is given by the following formula where I is the annual interest rate as a floating-point number:

    balance = P x (1 + I/Q) to the (N x Q) power. I have to write a program that inputs the values for P, I, Q, and N and outputs the balance for each year up through year N that uses a value-returning function to compute the balance and also prompts the user. Here is my code so far. Can someone tell me if I'm taking the right route or what else I need to do.

    // Algorithm
    // (1) Get input value for principal amount
    // (2) Get annual interest rate
    // (3) Get amount of times per year interest rate is compounded
    // (4) Get amount of years interest is to be compunded
    // (5) Use a value returning function to compute the balance
    // (6) Output values

    #include <iostream>
    #include <iomanip>

    float P, I, Q, N;

    int main()
    {
    cout.setf(ios::fixed,ios::floatfield);
    cout.setf(ios::showpoint);
    cout<<setprecision(2);

    cout<<"Enter principal amount"<<endl;
    cin>>P;
    cout<<"Enter annual interest amount"<<endl;
    cin>>I;
    cout<<"Enter amount of times interest is compunded per year"<<endl;
    cin>>Q;
    cout<<"Enter amount of years interest is to be compunded"<<endl;
    cin>>N;

    return P * (1 + (I / Q)^(N * Q);
    }

  2. #2
    geek SilentStrike's Avatar
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    Here is a tip, if you aren't absolutely sure it's in the langauge, don't use it. I had this problem before, and it made me really dislike programming. I had some experience with BASIC, and figured everything in BASIC should be in C++ as well. It will just add a lot of frustration. You need the pow in the <cmath> header to do this. In C++, this P * (1 + (I / Q)^(N * Q) looks like, also note that you were missing a closing paren.

    P * ( 1 + pow(I/Q, N*Q));
    Prove you can code in C++ or C# at TopCoder, referrer rrenaud
    Read my livejournal

  3. #3
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    Would this code work for what I wanted the program to do?

    // Algorithm
    // (1) Get input value for principal amount
    // (2) Get annual interest rate
    // (3) Get amount of times per year interest rate is compounded
    // (4) Get amount of years interest is to be compounded
    // (5) Use a value returning function to compute the balance
    // (6) Output balance value

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

    float P, I, Q, N;

    int main()
    {
    cout.setf(ios::fixed,ios::floatfield);
    cout.setf(ios::showpoint);
    cout<<setprecision(2);

    cout<<"Enter principal amount"<<endl;
    cin>>P;
    cout<<"Enter annual interest amount"<<endl;
    cin>>I;
    cout<<"Enter amount of times interest is compunded per year"<<endl;
    cin>>Q;
    cout<<"Enter amount of years interest is to be compunded"<<endl;
    cin>>N;

    return P * (1 + pow(I/Q),N*Q));
    }

  4. #4
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    Guest
    I don't think you want to return the answer, return is there to tell the os if the program ran succesfully or not. Just use cout to show the answer instead.

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