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hijenny · 发表于 2010-7-20 06:35:10

想請問ˋ戰友( )裡的文字我目前看到是看不看沒有影響
你們覺得呢?
因為我常被誤導
例
A certain law firm consists of 4 senior partners and 6 junior partners.How many different groups of 3 partners can be formed in which at least one member of the group is a senior partner?(Two groups are considered different if at least one group member is different.)

(A) 48

(B) 100

(C) 120

(D) 288

(E) 600

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【答案】B

【思路】

團體裡至少有一位senior組合=團體所有組合－團體裡皆是三位junior的組合

10取3減6取 3 可是就是因為這句(Two groups are considered different if at least one group member is different.) 我又減了4取3
難道我會錯意了嗎?
或者能不能乾脆不看呢?
謝謝

(Two groups are considered different if at least one group member is different.) 我又減了4取3
難道我會錯意了嗎?
或者能不能乾脆不看呢?
謝謝

xiaomimi · 发表于 2010-7-20 08:26:26

献上我的答案：
三个人中至少有一个senior的选法是：
C(4,1)*C(6,2) + C(4,2)*C(6,1)+C(4,3)
=60+36+4
=100
since at least one senior, the outcome should be one senior with two junior, or two senior with one junior or all 3 junior.
This is combination. If it is possibility, you can go with 1-no senior. Please not mix these together.

xiaomimi · 发表于 2010-7-20 08:27:06

all three senior, sorry, typo.

hijenny · 发表于 2010-7-29 21:37:01

小妹不才
以我的理解

(Two groups are considered different if at least one group member is different.)

是說裡面不能有完全一樣的至少要有一個不同的
我的問題在那 (cˋ4, 3)
我原本算對
後來又扣掉了= =
我會錯意了嗎???????????????

hijenny · 发表于 2010-7-30 07:33:00

頂起來

yzg1236 · 发表于 2010-7-30 08:46:33

小妹不才
以我的理解

(Two groups are considered different if at least one group member is different.)

是說裡面不能有完全一樣的至少要有一個不同的
我的問題在那 (cˋ4, 3)
我原本算對
後來又扣掉了= =
我會錯意了嗎???????????????

-- by 会员 hijenny (2010/7/29 21:37:01)

你是理解的有问题，
红色的部分，你再解释一下，我没太明白你的意思

hijenny · 发表于 2010-7-31 06:37:39

Two groups are considered different if at least one group member is different.)

這句話的意思是不是說junior senior都至少要有一個人在那三個 partner裡??

hijenny · 发表于 2010-8-2 05:47:38

頂起來

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