Hours & Minutes difference between 2 dates is not correct

Hours & Minutes difference between 2 dates is not correct

End Date is
03-06-2011 05:30:00 PM

Start Date is
03-06-2011 08:47:11 AM

Formula that i'm using (saw on the forum board) is
((("Ready for Dispatch"-"Correct Data/CSV Received Time")  /  (1000 * 60 * 60)))

The result i'm getting is 
0.0245247....

Whereas it should be
08:43 in HH:mm format