ceteriz

divde the 12 balls into 3 sets of 4. 6 e$ R5 Z) u% k9 p/ O$ g
weight any 2 sets.' x/ N2 O. P  k3 G" H. e
if the 2 sets are equal, then you know the heavy one is in the third5.39.217.77:8898( y- |4 k, I; c* R' S$ y
if one of the 2 is heavier, then the heavy one is in that set
: l% o2 B0 f) q+ ?) ~; O- Qthen divide the 4 balls into 2.5.39.217.77:8898' h4 p' @9 [9 L5 S1 c" y
weigh them
5 W3 g! Z4 W6 U" F* p5.39.217.77:8898and divide the heavier into 1
/ L" A4 u6 N- ^( y9 h6 g, Q8 k  O公仔箱論壇and weight them.
' e, Z( o% P# x% _- l! w% s" h5.39.217.77:88983 x weighing and get the ans.  9 Q# P, z- A% P  F4 i* f  Q
in less than 15 secs.