Help in finding GCD correctly

Question

Hi,
I need to convert 39.8 to inches as 3' - 3 4/5".
For this, first I find the gcd of 8 and 10, which should be 2 and then divide 8 and 10 by 2 to get 4 and 5. I implemented following program, but it seems I am going wrong somewhere and it is not getting the correct result. I am not sure where I am going wrong, hence seeking your help.
{code}
public static void main(String[] args) {
          double decNum = 39.8d;
          int feet = (int)(decNum / 12); // 3
          int inch = (int)(decNum % 12); //3
          double fraction = decNum % 12; //3.8
          double remainderInch = (fraction - inch); //0.8
          String str = Double.toString(remainderInch);//0.8
          int numberOfDecPts = str.length() - 2;
          double tens = Math.pow(10, numberOfDecPts);
          long remainderWhole = (long)(remainderInch * tens);
          long gcd = builtInMethod(remainderWhole, (long)tens);
          double numerator = remainderWhole / gcd;
          double denominator = tens / gcd;
          StringBuffer sb = new StringBuffer();
          sb.append(feet + "\'" + " - ");
          sb.append(inch + " ");
          sb.append(numerator + "\\" + denominator + "\"");
          System.out.println(sb);
     public static long builtInMethod (long u, long v) {
     BigInteger bigU = new BigInteger (Long.toString (u));
     BigInteger bigV = new BigInteger (Long.toString (v));
     long gcd = bigU.gcd (bigV).longValue ();
     return gcd;
The GCD that I get is 4 instead of 2 and the ouput I get is:-
3' - 3 1.999999999999993E15\2.5E15"
It works perfectly for number like 39.5 (3' - 3 1.0\2.0") but not for 39.8.
If you could please suggestion where I am going wrong, that would be very helpful.
Thanks in advance!                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

Answer 1

Here is my convoluted way to coax a fraction out of decimal part
                double number=3.84;
          String str=""+number;
          System.out.println(str);
          int num=0;
          for(int i=0;i<str.length();i++)if(str.charAt(i)=='.'){
               num=Integer.parseInt(str.substring(i+1,str.length()));
               break;
          str=""+num;
          int den=(int)Math.pow(10,str.length());
          for(int i=den;i>1;i--){
               if(den%i==0 && num%i==0){
                    den=den/i;
                    num=num/i;
                    break;
          System.out.println((int)number+" "+num+"/"+den);