Question

If ${}^n{C}_{12}={}^n{C}_8$ then $n$ is equal to

• A. $6$
• B. $12$
• C. $26$
• D. $20$

Answer 1

The correct option is D $20$

${}^n{C}_{12}{=}^n{C}_8$
$\Rightarrow {}^n{C}_{12}={}^n{C}_{n-8}(\because {}^n{C}_r={}^n{C}_{n-r})$
$\Rightarrow 12=n-8$
$\Rightarrow n=20$