Answer this cool puzzle (CAT Question)

A man wanted to enter an  exclusive club but did not know the
password
that
was required. He waited by the  door and listened.



A club member knocked on  the door and the doorman said, "twelve."
The
member replied, "six " and was let  in.



A second member came to  the door and the doorman said, "six." The
member
replied, "three" and was let  in.



The man thought he had  heard enough and walked up to the door. The
doorman
said ,"ten" and the man  replied, "five."

But he was not let in.  What should have he said?



Comon guys, put on your  thinking caps & get the solution......