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GMAT Probabiliity

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Source: — Problem Solving |

Re: GMAT Probabiliity

by logitech » Thu Nov 20, 2008 1:49 am
moneyman wrote:Pls explain
I am not sure whether I understood the question but:

5 people in a circle can sit (n-1)! ways

4! = 24 ways
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Re: GMAT Probabiliity

by sudhir3127 » Thu Nov 20, 2008 1:59 am
logitech wrote:
moneyman wrote:Pls explain
I am not sure whether I understood the question but:

5 people in a circle can sit (n-1)! ways

4! = 24 ways
even i go with 24..

formula " N people arranged in a circle js ( n-1)!
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by vishubn » Thu Nov 20, 2008 9:51 am
one more vote for 24
Circular arrangement (n-1)! --- 4! =24

Vishu
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by jackcrystal » Thu Nov 20, 2008 7:41 pm
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by logitech » Thu Nov 20, 2008 7:43 pm
jackcrystal wrote:24
wow thanks. So next time I see a question like this I will remember your "24".

Awesome!
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by cramya » Thu Nov 20, 2008 7:47 pm
Logitech,
Remember my 24 too

24 :-)

I have added the smilies at the end just for u man.(so that u can rememeber in a happy state)
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by logitech » Thu Nov 20, 2008 7:57 pm
cramya wrote:Logitech,
Remember my 24 too

24 :-)

I have added the smilies at the end just for u man.(so that u can rememeber in a happy state)
:wink: Dear Diary, there are so many funny guys in this forum. One of them is called Cramya ;-)
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by jimmiejaz » Fri Nov 21, 2008 9:12 am
Guys, the question just gave the definition of a circular permutation in a tricky way. It says the arrangement is different only when the guys position is changed relative to one another.

And in circular permutation, the position relative to one another is same clockwise or anticlockwise.
So, it just asks the no of arrangements in a circular permutation and that is indeed 24 as explained by logitech.

Hope it helps!!!!
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I think about it like this

by GMATters1001 » Fri Nov 21, 2008 11:51 am
Not knowing the formula for circular permutations:

5 people can be arranged 5! ways, however, since their relation to one another doesn't matter means that for every arrangement, there will be 4 others (5 total i.e. seats at the table) that are considered the same. thought of as an anagram,
12345 is the same as:
51234
45123
34512
23451

so the answer is 5! ways, divided by 5 that are considered the same=120/5=24.
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Re: I think about it like this

by orel » Sat Nov 22, 2008 1:56 am
GMATters1001 wrote:Not knowing the formula for circular permutations:

5 people can be arranged 5! ways, however, since their relation to one another doesn't matter means that for every arrangement, there will be 4 others (5 total i.e. seats at the table) that are considered the same. thought of as an anagram,
12345 is the same as:
51234
45123
34512
23451

so the answer is 5! ways, divided by 5 that are considered the same=120/5=24.
Hello guys,
is the formula always the same for circular arrangements: (n-1)! ?

and would the correct answer be 120, if the qustion asked to find the number of arrangements for 5 people on a round table?
thanks,
Feruza
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by lunarpower » Mon Nov 24, 2008 5:10 am
the difference between a round table and a normal table is that a round table has no ends. therefore, you can arbitrarily select which seat is to be called seat #1.
two ways to approach this problem:

(1)
you can fix one of the people in place (or, equivalently, rotate the table like a carousel so that that person always winds up in the same place). this will avoid the production of multiple equivalent scenarios in which the people are seated in the same order, but have just shuffled a seat or two over (these don't count as different arrangements).
then you have free rein to arrange the other four people, so that's 4! = 24 arrangements.

(2)
alternatively, you can figure out that there are 5! = 120 arrangements overall.
however, each UNIQUE arrangement is actually repeated five times: because there are five seats at the table, there are 5 different versions of every possible seating arrangement. (for instance, ABCDE, BCDEA, CDEAB, DEABC, EABCD are all equivalent.)
so this means you must divide by 5: 120 / 5 = 24
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