Hi guys, The question is $\displaystyle 7Pn=42$ from here i changed to $\displaystyle \7!(7-n)!=42$ and crossed multiplied giving me the wrong answer the right answer however is two how do we do these?

Printable View

- Jun 12th 2013, 02:30 PMGurp925Permutation question!
Hi guys, The question is $\displaystyle 7Pn=42$ from here i changed to $\displaystyle \7!(7-n)!=42$ and crossed multiplied giving me the wrong answer the right answer however is two how do we do these?

- Jun 12th 2013, 02:36 PMtopsquarkRe: Permutation question!
- Jun 12th 2013, 02:50 PMPlatoRe: Permutation question!
- Jun 12th 2013, 02:59 PMGurp925Re: Permutation question!
love Plato's method answer = 2 yay! and once we get to this portion $\displaystyle 7!=42(7-n)!$ how do we get the answer two from here ?

- Jun 12th 2013, 03:16 PMPlatoRe: Permutation question!
- Jun 12th 2013, 08:36 PMibduttRe: Permutation question!
Plato has explained very well. However we can also proceed as under

7! = 42 * ( 7-n)!

7*6* 5! = 42 * ( 7-n)!

5! = ( 7-n)!

that gives 7-n=5 OR n = 2 - Jun 12th 2013, 11:55 PMGurp925Re: Permutation question!
Great answers thanks so much guys.