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Divide 3 groups first.5.39.217.778 J: V3 ?5 {! p+ H: K1 u9 W
i.e. 4 x 4 x 4.
  N0 Q" a# m, I5.39.217.77Weight any 2 groups [1st]
  p$ P: g+ d3 ~1 q5.39.217.77then you will know the heavier ball in which group.. k9 f$ T/ J: ^+ @. J# K
Weight any 2 balls in that group [2nd]公仔箱論壇1 O1 p# f/ q* s7 H
then you will know the heavier ball in which 2 balls.
; @5 b" |" s! v* e7 s1 M公仔箱論壇Repeat again in remainders [3rd]( S, ^! w' j5 l4 T0 f
Got the heavier ball.