Question

I’m creating a program where the kids must convert a decimal value (I.E. 0.xxxx – precision 4) to a fraction.

I need to know whether a fraction terminates or not, I mean:

1/9 ~ 0.111 but 111/1000 = 0.111

I’m creating a Fraction class, but I have no idea how to distinguish between these two cases.

public class Fraction
{
    #region Fields

    private int _numerator;
    private int _denominator;

    #endregion

    #region Properties

    public int Numerator
    {
        get { return _numerator;}
        set { _numerator = value;}
    }

    public int Denominator
    {
        get { return _denominator;}
        set { _denominator = value;}
    }

    public decimal DecimalValue
    {
        get { return (decimal)_numerator / _denominator; }
    }

    #endregion

    #region Constructors

    public Fraction() { }
    public Fraction(int numerator, int denominator)
    {
        this.Numerator = numerator;
        this.Denominator = denominator;
    }

    #endregion
}

Can you help me?
Thanks in advance.

Answer 1

Find the denominator’s prime factorization.

If all the prime factors are either 2 or 5, it will have a finite decimal representation.

If it has a prime factor that is not 2 or 5, then it will be a recurring decimal.

(It works because 10’s prime factors are 2 and 5.)

edit – And check that numerator % denominator is not 0, as Stefan H points out.