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请教解数学题。

灰衣人 2010-09-06 18:14:36 ( reads)

We have 20 thousand dollars that must be invested among 4 possible opportunities. Each investment must be integral in units of 1 thousand dollars.
How many different investment strategies are possible?
What if not all money need be invested?

跟帖(22)

guest1000

2010-09-07 11:30:28

回复：请教解数学题。

guest1000

2010-09-07 19:44:24

回复：回复：请教解数学题。

guest1000

2010-09-07 19:51:53

回复：回复：回复：请教解数学题。

皆兄弟也

2010-09-08 09:10:55

第二题答案是不是:C(16+3,3)+C(15+3,3)+...+C(1+3,3)+C(0+3,3)

jinjing

2010-09-08 09:35:30

I think we should change 16 to 20....we get C(24,4)=...

皆兄弟也

2010-09-08 10:00:33

how to understand: must be invested among 4 possible opportuniti

皆兄弟也

2010-09-08 10:03:46

even if we should change 16 to 20....we get C(21,4)=...

皆兄弟也

2010-09-08 10:07:18

sorry, C(21,4)=... wrong; C(24,4)=... right,if we should change

皆兄弟也

2010-09-08 10:09:50

you are right:C(20,4)=C(16+3,3)+C(15+3,3)+...+C(1+3,3)+C(0+3,3)

皆兄弟也

2010-09-08 10:37:04

第二题:What if not all money need be invested? 可这样理解：

皆兄弟也

2010-09-08 09:03:17

我认为，您的第一题答案是正确的。

guest1000

2010-09-08 12:31:24

回复：我认为，您的第一题答案是正确的。

皆兄弟也

2010-09-08 13:03:14

yes,您的第二题答案是正确的,as well。

皆兄弟也

2010-09-08 13:17:31

Put 16 balls in 5 bins, no matter 5 bins can be empty or not, wh

jinjing

2010-09-07 18:19:35

Recursive functions for several variables.

guest1000

2010-09-07 20:04:56

回复：请教解数学题。

jinjing

2010-09-07 21:39:24

first Q : 969 second Q:10626

guest1000

2010-09-08 12:23:06

回复：first Q : 969 second Q:10626

jinjing

2010-09-08 13:10:35

I mean second Q; We can put 0 for 4 cases.So, the

wuliwuwai

2010-09-09 11:52:38

"1536" - 没上过大学, 用俺的高中知识试着解1解

wuliwuwai

2010-09-09 12:04:38

sorry, should be "1513"

jinjing

2010-09-09 19:53:17

不懂,4! 不可以,因可能有相同的钱.请说明您的思路.