permuation on circles

gocanucks

I have got a question on permutation on circles. Say there are 5 slots, and we want to place 5 balls (different colors). What should be the correct answer? P(5) or P(5)/2.

I guess the answer depends on how one interprets whether clockwise is the same as counter-clockwise direction. What is the general assumption under GMAT? I have seen different JJ giving different answers depending on different interpretations.

isuffering

I see,  thanks.

robert

这道题答案应该是 P(5)/5=P(4)

isuffering

Disucussion:

I think there're 2 tricks:

If  not sonsider cloclwise or counter clockwise,

remember, it's a circle, so the ABCDE,BCDEA,CDEAB,DEBAC,EABCD is the same permutation,

then should be  P(5)/5== P(4)

And
if consider cloclwise or counter clockwise,

then should be P(4)/2


Whether the clockwise permutation is considered different from or the same as  the counter-clockwise permutation under the Gmat ?
It's really a question.

Hope somebody can give an confirm answer.

Looking forward to discussion!

[此贴子已经被作者于2003-6-6 0:39:53编辑过]

Echo

和方向无关，P(5)