Question

${}^n{P}_r$ and ${}^n{C}_r$ are equal when:

• A. $n=r$
• B. $n=r+1$
• C. $r=1$
• D. $n=r-1$

Answer 1

Answer: (C)

$r=1$

For ${}^n{P}_r{=}^n{C}_r$ to be equal,
$\Rightarrow \frac{n!}{(n-r)!}=\frac{n!}{(n-r)!r!}$

$\Rightarrow r!=1$

$\Rightarrow r=0,1$