ceteriz

divde the 12 balls into 3 sets of 4. ' T) a, _' l5 b; T. }" v
weight any 2 sets.
# ~; x8 W9 a, X) a( p. @4 ~- I, cTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。if the 2 sets are equal, then you know the heavy one is in the third
  ~$ f$ t# O: J. Z$ VTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。if one of the 2 is heavier, then the heavy one is in that set
  A2 o9 n, o) V) w8 tthen divide the 4 balls into 2.: i# [4 g0 d' T# d! O  E! M
weigh them
3 Q6 S% d- c6 m- Yand divide the heavier into 1tvb now,tvbnow,bttvb& ~8 s# N: q6 ]: O" B4 _# i+ x3 h0 l
and weight them., M  ~3 G0 v. P, @
3 x weighing and get the ans.  ' ^: E2 p, G$ o8 `# F
in less than 15 secs.