Question

if 12Pr=1320 then find r

Answer 1

Hey here is your answer..

12Pr =1320
r = 1320/12p
r = 110 × p

Answer 2

Answer:

Hence the correct answer is $3$.

Step-by-step explanation:

Given:- ${^{12}{P}_{r}} = 1320$

To find:- $r = ?$

As we know that,

${^{n}{P}_{r}} = \cfrac{n!}{\left( n - r \right)!}$

Therefore,

${^{12}{P}_{r}} = 1320$

$\cfrac{12!}{\left( 12 - r \right)!} = 1320$

$\left( 12 - r \right)! = \cfrac{12 \times 11 \times 10 \times 9!}{12 \times 11 \times 10} \; \left( \because 1320 = 12 \times 11 \times 10 \right)$

$\left( 12 - r \right)! = 9!$

$12 - r = 9$

$r = 12 - 9 = 3$

Hence the value of $r$ is $3$