The number of ways in which ten candidates A1,A2 , .......,A10 can be ranked , if A1 is always above A2 , is

Answers (1)

Solution:    The ten candidates can be ranked in 10! ways

                    In half of these  A_1  is ranked above A_2 and half

                    of  these A_2 is ranked  above A_1.

                    The desired number is frac10!2=5cdot 9!

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