Having trouble with compound interest program
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Thread: Having trouble with compound interest program

  1. #1
    Join Date
    Feb 2011
    Posts
    1

    Unhappy Having trouble with compound interest program

    namespace ConsoleApplication1
    {
    class Program
    {
    static void Main(string[] args)
    {
    //prompt user to enter principal
    Console.WriteLine( "enter principle:");
    string principalInput = Console.ReadLine();
    double principal = Convert.ToDouble(principalInput);
    //make sure princiapl is not negative
    if (principal < 0)
    {
    Console.WriteLine("Principal cannot be negative");
    principal = 0;
    }
    //enter intrest rate
    Console.WriteLine("enter intrest rate");
    string intrestInput = Console.ReadLine() ;
    double intrest = Convert.ToDouble(intrestInput);
    //make sure intrest is not negative.
    if (intrest < 0)
    {
    Console.WriteLine("intrest cannot be negative");
    intrest = 0;
    }
    //calculate the value of principal plus intrest.
    double intrestPaid= principal*(intrest/100);
    //now calculate the total
    double total = principal + intrestPaid;
    // output the result
    Console.WriteLine();//skip a line
    Console.WriteLine("principal =" +principal);
    Console.WriteLine("Intrest ="+ intrest + "%");
    Console.WriteLine();
    Console.WriteLine("intrest paid =" +intrestPaid);
    Console.WriteLine("Total =" +total);
    Console.WriteLine("If you want compound intrest enter the number of years,if not close now");
    string years1=Console.ReadLine();
    double years2 = Convert.ToDouble(years1);
    double CompoundIntrest = principal * ((double)Math.Pow(1.0+intrest, years2));
    Console.WriteLine("Compound intrest is" +CompoundIntrest);
    //Wait for response then tell the user how to leave
    Console.WriteLine ("Press Enter to Terminate...");
    Console .Read() ;
    I beleive the error here is that i have used Math.Pow which is what my friend has told me to use
    the purpose i to figure out a compound intrest so if the princaple is 100 and teh intrest 10 and years is 2 i should get 121
    can somebody rewrite this for me and tell me what would work
    thank you forums

  2. #2
    Join Date
    Feb 2011
    Location
    United States
    Posts
    1,006

    Re: Having trouble with compound interest program

    You are very close and even have identified the correct line that is in error.

    Code:
    double CompoundIntrest = principal * ((double)Math.Pow(1.0+intrest, years2));
    Look carefully at the value stored in intrest (hint: it shouldn't be > 1). To compound at, say, 30 percent interest you would perform the following calculation:

    Principle * (1.3)^(years)

    Does that make it clear now you need to modify the program? Try some things and if you still have problems let us know.

    Also, this is unrelated: Also Math.Pow returns a double, so you don't need to use a cast.
    Best Regards,

    BioPhysEngr
    http://blog.biophysengr.net
    --
    All advice is offered in good faith only. You are ultimately responsible for effects of your programs and the integrity of the machines they run on.

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