Question

${}^n{\text{C}}_r=\frac{n!}{(n-r)!\times r!}$ is applicable only when

• A.
  $r\le n$
• B.
  $0\le r\le n$
• C.
  $0<r\le n$
• D.
  All of the above.

Answer 1

The correct option is B

$0\le r\le n$
${}^n{\text{C}}_r=\frac{n!}{(n-r)!\times r!}$ is applicable when $0\le r\le n$.