請教解數學題。

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?

所有跟帖： 

• 回複：請教解數學題。 -guest1000- ♂ (1042 bytes) () 09/07/2010 postreply 11:30:28

• 回複：回複：請教解數學題。 -guest1000- ♂ (364 bytes) () 09/07/2010 postreply 19:44:24

• 回複：回複：回複：請教解數學題。 -guest1000- ♂ (45 bytes) () 09/07/2010 postreply 19:51:53

• 第二題答案是不是:C(16+3,3)+C(15+3,3)+...+C(1+3,3)+C(0+3,3) -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 09:10:55

• I think we should change 16 to 20....we get C(24,4)=... -jinjing- ♀ (0 bytes) () 09/08/2010 postreply 09:35:30

• how to understand: must be invested among 4 possible opportuniti -皆兄弟也- ♂ (81 bytes) () 09/08/2010 postreply 10:00:33

• even if we should change 16 to 20....we get C(21,4)=... -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 10:03:46

• sorry, C(21,4)=... wrong; C(24,4)=... right,if we should change -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 10:07:18

• 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- ♂ (0 bytes) () 09/08/2010 postreply 10:09:50

• 第二題:What if not all money need be invested? 可這樣理解： -皆兄弟也- ♂ (271 bytes) () 09/08/2010 postreply 10:37:04

• 我認為，您的第一題答案是正確的。 -皆兄弟也- ♂ (265 bytes) () 09/08/2010 postreply 09:03:17

• 回複：我認為，您的第一題答案是正確的。 -guest1000- ♂ (327 bytes) () 09/08/2010 postreply 12:31:24

• yes,您的第二題答案是正確的,as well。 -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 13:03:14

• Put 16 balls in 5 bins, no matter 5 bins can be empty or not, wh -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 13:17:31

• Recursive functions for several variables. -jinjing- ♀ (486 bytes) () 09/07/2010 postreply 18:19:35

• 回複：請教解數學題。 -guest1000- ♂ (251 bytes) () 09/07/2010 postreply 20:04:56

• first Q : 969 second Q:10626 -jinjing- ♀ (90 bytes) () 09/07/2010 postreply 21:39:24

• 回複：first Q : 969 second Q:10626 -guest1000- ♂ (68 bytes) () 09/08/2010 postreply 12:23:06

• I mean second Q; We can put 0 for 4 cases.So, the -jinjing- ♀ (19 bytes) () 09/08/2010 postreply 13:10:35

• "1536" - 沒上過大學, 用俺的高中知識試著解1解 -wuliwuwai- ♀ (181 bytes) () 09/09/2010 postreply 11:52:38

• sorry, should be "1513" -wuliwuwai- ♀ (120 bytes) () 09/09/2010 postreply 12:04:38

• 不懂,4! 不可以,因可能有相同的錢.請說明您的思路. -jinjing- ♀ (0 bytes) () 09/09/2010 postreply 19:53:17