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divde the 12 balls into 3 sets of 4.
& ?/ n7 L  }6 j  e  L公仔箱論壇weight any 2 sets.
7 I9 y! x2 {9 \4 `; U5.39.217.76if the 2 sets are equal, then you know the heavy one is in the third
% X' t+ N9 Q) o. m; R5 o5.39.217.76if one of the 2 is heavier, then the heavy one is in that set
" i$ z8 r! [8 \2 Y. M) l公仔箱論壇then divide the 4 balls into 2.5.39.217.769 k; a0 v; K$ w7 p( k6 r
weigh them
1 P$ f0 f% \7 Z) }2 |) b6 Q' ltvb now,tvbnow,bttvband divide the heavier into 1
* j; p! a& k! I0 N4 Dand weight them.; w1 `: Y2 E/ d/ `% Z# m5 Q( i/ J4 u# P
3 x weighing and get the ans.  公仔箱論壇$ f, P! P; _1 O3 u
in less than 15 secs.