i thing the answer is公仔箱論壇0 a9 F2 A% a& Q# A4 S
start with 4 on each side of the scale,this will have two possible outcome, same or diff.公仔箱論壇( V3 r+ P2 ?$ |4 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. |