Word of length 10 are formed using the letters A,B,C,D,E,F,G,H,I,J. Let `x` be the number of such words where no letter is repeated; and let `y` be the number of such words where exactly one letter is repeated twice and no other letter is repeated. The, `y/(9x)=`

Explanation

x=number of such word where number letter is expected

`x=10!`

y= the number of such words where exactly one letter is repeated .

`y=.^10C_1*.^9C_8*(10!)/(2!)`

`y/(g(x))=(.^10C_1*.^9C_8*(10!)/(2!))/(9*10!)`

`y/(g(x))=5`.