转一个微软的 brain teaser

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送交者: 匆匆过客于 2006-09-29, 13:45:24:

每个飞机只有一个油箱，飞机之间可以相互加油。一箱油可供一架飞机绕地球飞半圈。

问题：为使至少一架飞机绕地球一圈回到起飞时的飞机场，至少需要出动几架飞机？（所有飞机从同一机场起飞，而且必须安全返回机场，不允许中途降落，中间没有飞机场）

所有跟贴:

老题目了是数学竞赛中我比较喜欢的一题 (无内容) - Jingyi (0 bytes) 2006-10-02, 17:58:38 (105492)
四架可以了 - tang (766 bytes) 2006-09-29, 20:45:39 (105224)
- 两架就够了：) - 插一腿 (67 bytes) 2006-09-29, 21:52:06 (105228)
  - 那叫起双飞 (无内容) - Latino2 (0 bytes) 2006-09-30, 12:23:07 (105282)
  - 5架 (无内容) - 4U4luC2 (0 bytes) 2006-09-30, 00:17:50 (105242)
    - 3架飞机5架次,土库是对的. - shine (156 bytes) 2006-09-30, 07:27:36 (105261)
      - 不是俺算的. (无内容) - shine (0 bytes) 2006-09-30, 07:30:40 (105262)
  - 一架就够了 - whoami (94 bytes) 2006-09-29, 23:16:33 (105235)
无速度限制.2架. (无内容) - fe2004 (0 bytes) 2006-09-29, 19:05:05 (105208)
five is correct (无内容) - t1301520 (0 bytes) 2006-09-29, 18:14:33 (105206)
Depending on how the question is asked - outsider (178 bytes) 2006-09-29, 18:13:34 (105205)
5架. (无内容) - 星宿老怪 (0 bytes) 2006-09-29, 18:08:08 (105203)
6: 3 clockwise, 3 counter clockwise (无内容) - syw2000 (0 bytes) 2006-09-29, 17:51:59 (105201)
4架足够了 - conner (215 bytes) 2006-09-29, 17:35:36 (105199)
如果这题答错的话给踢出去，这个坛子就冷清多了。我的答案：10 - IhopeIamwrong (273 bytes) 2006-09-29, 15:42:06 (105176)
- you should be the first to be kicked out, three are just enough (无内容) - real_bingfeng (0 bytes) 2006-09-29, 23:48:46 (105237)
- 太多了 (无内容) - conner (0 bytes) 2006-09-29, 17:21:09 (105198)
Best answer: only one—dump unnecessary weight to add 2nd tank. (无内容) - AI (0 bytes) 2006-09-29, 15:28:09 (105167)
- No, that's against MS philosophy. You are fired (无内容) - outsider (0 bytes) 2006-09-29, 16:07:09 (105187)
Assuming filling tank is instantaneous, then 6 planes are needed - outsider (651 bytes) 2006-09-29, 15:15:55 (105155)
- If plane F is one of plane A,B,C, E - ping_max (27 bytes) 2006-09-29, 17:51:09 (105200)
  - That's true (无内容) - outsider (0 bytes) 2006-09-29, 18:09:39 (105204)
- ?? - ping_max (183 bytes) 2006-09-29, 15:56:56 (105181)
  - sorry , I think I am wrong. never mind (无内容) - ping_max (0 bytes) 2006-09-29, 15:57:42 (105182)
- I think this solution is better than mines. Damn, I know - wavelet (39 bytes) 2006-09-29, 15:55:33 (105180)
  - To MS, the more waste the better (无内容) - outsider (0 bytes) 2006-09-29, 16:12:41 (105191)
  - too sad, I am not smart enough to get into MS.... (无内容) - wavelet (0 bytes) 2006-09-29, 15:59:21 (105184)
- 你的答案比我知道的要好 - 匆匆过客 (79 bytes) 2006-09-29, 15:40:56 (105175)
  - Alright! I'm king of the xxxxx!!! :) (无内容) - outsider (0 bytes) 2006-09-29, 16:08:54 (105189)
    - 同中国的煤体有一拼 - 匆匆过客 (57 bytes) 2006-09-29, 16:25:02 (105194)
impossible - queue (70 bytes) 2006-09-29, 14:33:15 (105131)
- SOME REFILL PLANES CAN GO THE OTHER WAY OF A CIRCLE (无内容) - lee (0 bytes) 2006-09-29, 15:50:22 (105179)
3 (无内容) - 008 (0 bytes) 2006-09-29, 14:26:09 (105129)
my answer is 6 planes. is that correct? (无内容) - wavelet (0 bytes) 2006-09-29, 14:14:00 (105123)
- it's close - maybe you didn't count the one that finishes cirlcling the globe in - 匆匆过客 (31 bytes) 2006-09-29, 14:16:33 (105124)
  - Wrong - weiqjweiqj (709 bytes) 2006-09-29, 14:33:04 (105130)
    - item 3 looks erroneous - 匆匆过客 (93 bytes) 2006-09-29, 14:48:26 (105139)
    - you are wrong, then D, E can not fly back to home..:) - wavelet (58 bytes) 2006-09-29, 14:43:04 (105135)
      - Yeah! My bad! I am lousy at Math :) (无内容) - weiqjweiqj (0 bytes) 2006-09-29, 14:51:16 (105141)
        
        your math is fine. :-) - wavelet (59 bytes) 2006-09-29, 14:53:58 (105142)
  - right, I didn't count the one who finishs the circle (无内容) - wavelet (0 bytes) 2006-09-29, 14:24:17 (105128)
  - 6 is right, you said how many planes need to provide gas for 1 - wavelet (162 bytes) 2006-09-29, 14:22:00 (105127)
    - wait, at 90 it got full tank but it have to get 270 + 15 - 4U4luC2 (63 bytes) 2006-09-29, 15:16:17 (105156)
      - why it have to get 270+15? it can get fuel at 270 - wavelet (82 bytes) 2006-09-29, 15:20:08 (105159)
        
        no plane can reach 270 and still supply - 4U4luC2 (53 bytes) 2006-09-29, 15:21:57 (105160)
        
        You can however supply B with C's reminder at 300(3/1 tank) - 4U4luC2 (83 bytes) 2006-09-29, 15:27:17 (105166)
        
        no, you don't need to, here is the sane procedure: - wavelet (131 bytes) 2006-09-29, 15:31:50 (105169)
        
        right, I prviousely thought only two supplys - 4U4luC2 (75 bytes) 2006-09-29, 15:35:43 (105172)
        
        if you can understand B in the first set of 3, then you can - wavelet (45 bytes) 2006-09-29, 15:26:38 (105164)
        
        haha, the other set of 3 plane can fly from opposite direction - wavelet (24 bytes) 2006-09-29, 15:23:06 (105161)
        
        A' give B' 1/3 gas at degree 300, then B' can give 1/3 gas - wavelet (30 bytes) 2006-09-29, 15:24:17 (105162)
        
        thought we are talking about 5 planes :) (无内容) - 4U4luC2 (0 bytes) 2006-09-29, 15:30:16 (105168)
    - 不行，半程(1/4 global)的话所有飞机都要用剩余燃料返回， - 4U4luC2 (24 bytes) 2006-09-29, 14:39:02 (105133)
      - are you talking about my method? here is my details - wavelet (324 bytes) 2006-09-29, 14:48:12 (105138)
        
        AAA can't have full tank of fuel at degree 90 - 匆匆过客 (41 bytes) 2006-09-29, 14:57:31 (105145)
        
        AAA got 1/3 at 60 from B and 1/6 from C at 75 - 4U4luC2 (71 bytes) 2006-09-29, 15:02:01 (105149)
        
        no, last fueling at 90 degree by plane B. - wavelet (34 bytes) 2006-09-29, 14:58:50 (105147)
        
        right. i missed the refueling from plane b since it's so up there (无内容) - 匆匆过客 (0 bytes) 2006-09-29, 15:05:23 (105150)
        
        that works (无内容) - 4U4luC2 (0 bytes) 2006-09-29, 14:55:43 (105144)
3 (无内容) - lssc27 (0 bytes) 2006-09-29, 14:08:18 (105122)
5架，在1/6处和3/4处空中加油 (无内容) - weiqjweiqj (0 bytes) 2006-09-29, 14:05:41 (105121)
- Oops, 2/3 as well (无内容) - weiqjweiqj (0 bytes) 2006-09-29, 14:17:27 (105125)

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