第四题

kongfanqing

Nine Balls

You have nine balls, three of which are slightly heavier, and three of which are slightly lighter than the normal three. All three balls in each group have the same weight. All nine balls are identical otherwise. Your mission is to determine the group of every ball using a pair of scales.
- ?. x9 f4 [  S& q+ T* X
How many weighings are needed in order to ensure the accomplishment of your mission?
  @# j. `) w# H
; s- i; U7 Q; ANotes:
% x) i9 m) c9 J1. The difference of weight between the heavy and normal balls is not necessarily equal to the difference of weight between the light and normal balls.
6 a5 M7 S0 o7 [8 Z2. The scales show only which side is heavier; it does not show the difference of weight.

dcao

我基本上是采用看英语文章的办法，先泛读，再精读，再一句一句看，最后再提纲挈领，总算是明白一点了，当然，也可能还是领悟错了。最后要说的一句话是：楼主，你很牛叉，希望你不是真的有病。   

sunnyglm

留个脚印```````

sjjkingboy

顶顶更健康，越顶吃的越香。

ghjtxg

楼主，你写得实在是太好了。我惟一能做的，就只有把这个帖子顶上去这件事了

gfkdqz

楼主那种裂纸欲出的大手笔，竟使我忍不住一次次的翻开楼主的帖子……   

wzaaa

我来了~~~~~~~~~ 闪人~~~~~~~~~~~~~~~~  

villager

偶的天啊!这是什么样的贴子呢？

JEFSCE

楼主，你写得实在是太好了。我惟一能做的，就只有把这个帖子顶上去这件事了