The number of ways in which 10 candidates A1,A2,.....A10  can e ranked, so that A1  is always above A2  is

The number of ways of placing A1  and A2  in ten places so that A1  is always above A2  is C102.  There are 8! Ways of arranging the eight other candidates. Hence, total number of arrangementsC102×8!=10!2!8! 8!=10!2