# permutation

• Feb 18th 2013, 07:01 AM
kastamonu
permutation
There are 5 different pictures. We want to hange them on a wall. If we want a special one to be in the middle in how many ways we can hang them?
• Feb 18th 2013, 07:20 AM
Plato
Re: permutation
Quote:

Originally Posted by kastamonu
There are 5 different pictures. We want to hange them on a wall. If we want a special one to be in the middle in how many ways we can hang them?

What are your ideas on this model?
• Feb 18th 2013, 08:33 AM
MINOANMAN
Re: permutation
Kastamonu
this an easy question . If one photo is your favourite then pick-it up and fix the remaining 4....you have as many choices as the permutations for 4 photos are. i.e 4!...easy....
• Feb 18th 2013, 08:38 AM
Plato
Re: permutation
Quote:

Originally Posted by MINOANMAN
Kastamonu
this an easy question . If one photo is your favourite then pick-it up and fix the remaining 4....you have as many choices as the permutations for 4 photos are. i.e 4!...easy....

@MINOANMAN, Why did you not let the student answer my request?
You spoiled the chance that user Kastamonu might learn by doing.
• Feb 18th 2013, 09:14 AM
kastamonu
Re: permutation
I did the samething but according to my book the answer is 48. 2 pictures from 4 can be chosen in 1/2p(4,2)=6 ways. they change places between themselves and this is 2! and this öakes 12. The other 2 pictures change places between themselves 2!. 12.2! is 24. If we think 4 pictures as 2 seperate groups : 24.2!=48.
• Feb 18th 2013, 10:33 AM
Plato
Re: permutation
Quote:

Originally Posted by kastamonu
I did the samething but according to my book the answer is 48. 2 pictures from 4 can be chosen in 1/2p(4,2)=6 ways. they change places between themselves and this is 2! and this öakes 12. The other 2 pictures change places between themselves 2!. 12.2! is 24. If we think 4 pictures as 2 seperate groups : 24.2!=48.

That textbook is wrong.
If I were you, I would file a complaint with your educational authority about that poor text and or instructor.