ceteriz

divde the 12 balls into 3 sets of 4. 5.39.217.77+ U8 e3 u1 m8 R$ ~4 Z
weight any 2 sets.
% Z; t2 k$ F/ y5 q/ D6 h公仔箱論壇if the 2 sets are equal, then you know the heavy one is in the third
5 j1 P7 V) j# A" uif one of the 2 is heavier, then the heavy one is in that set
  l8 d) q1 f5 m* R4 R6 b4 jtvb now,tvbnow,bttvbthen divide the 4 balls into 2.5.39.217.77% s' u/ z& t5 q
weigh them7 D3 }, s, G. W2 n2 n, N
and divide the heavier into 1tvb now,tvbnow,bttvb  H9 A- w7 d1 f9 M- z9 A
and weight them.
  u1 `( M5 [, h/ ptvb now,tvbnow,bttvb3 x weighing and get the ans.  & n6 T- U. ~: n: e/ I
in less than 15 secs.