Question

Number of ways to divide $21$ different things into two groups of $10$ and $11$ things are?

• A. $\frac{21!}{8!\times 10!}$
• B. $\frac{21!\times 10!}{11!}$
• C. $\frac{21!}{8!\times 11!}$
• D. $\frac{21!}{10!\times 11!}$

Answer 1

The correct option is D $\frac{21!}{10!\times 11!}$

To divide n different things into two different sized groups of $m$ and $q$ is=$\frac{n!}{m!\times q!}$
here, $n=21$
$m=10$
$q=11$
Therefore, answer =$\frac{21!}{10!\times 11!}$
option (d) is correct