math problem

[Doctor PJ]

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How many arrangements can 6 people be seated around a circular table? Answer is 120, but shouldn't it be 720? 6!

 

[ddsbruin]

Quick formula for "how many ways around a round table" probability questions is (n-1)! so 6-1 = 5! = 120

 

[Doctor PJ]

thanks bruin, didn't know that till now!🙂

 

[joonkimdds]

it doesn't say how many chairs are available. if it says only 5 chairs are available, the method of getting the answer would be totally different.

 

[Streetwolf]

Quick formula for "how many ways around a round table" probability questions is (n-1)! so 6-1 = 5! = 120

Quick formula is (nPr) / r where r is the number of seats. In many cases you actually have n = r and this reduces the problem down to (n-1)!.

 

[ddsbruin]

Thanks streetwolf, use his formula. mine was only good for as he said when n=r.