ceteriz

divde the 12 balls into 3 sets of 4. : {8 O8 R' Q6 h$ `
weight any 2 sets.
! j. x4 V8 B4 f/ ]$ Aif the 2 sets are equal, then you know the heavy one is in the third' B" [* g* H3 R. _  d  f0 o
if one of the 2 is heavier, then the heavy one is in that set
: d) F( m  W" d2 ^  O+ r* i$ H  Vthen divide the 4 balls into 2.
8 g+ @2 t2 R, f, x) j) T5 eweigh them公仔箱論壇' @, T2 x* l% I# [, T2 j
and divide the heavier into 1tvb now,tvbnow,bttvb& h# t& j( K- D/ {* g
and weight them.: s. A0 q2 [, \, d2 `2 y
3 x weighing and get the ans.  公仔箱論壇- D6 c" d) z, H! V( Y/ v
in less than 15 secs.