i thing the answer is
2 T& N1 K* {% d3 ^. @5 i- u' H( N公仔箱論壇start with 4 on each side of the scale,this will have two possible outcome, same or diff.公仔箱論壇) j+ y8 s* Z0 F$ v5 u
If the same then 4 that left over contain the odd ball. put 1 of the 4 to each side, two outcome, same or different again. Replace 1 from the remaining, if the same then left over is the odd or if different the replacement is the odd one. I didn't time myself but I think I take less than 30 minutes. There are two more possible out come but still need three weighing but I think I am running out of space. |