Question

If n boys and n girls sit along a line alternately in x ways and along a circle alternately in y ways such that $x=12y$ then n is equal to

• A. $6$
• B. $8$
• C. $9$
• D. $12$

Answer 1

The correct option is A $6$

$x=n!n!\times 2$
$y=(n-1)!n!$
now its given that $x=12y$
$\therefore 2.n!n!=12(n-1)!n!$
$⟹n=6$