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12 balls part 2
Better solution. there are 12 balls which can be divided in two groups and weigh them. the lighter one contains the 9 gm ball and then pick the lighter one and further divide it into a group of 3 balls. now weigh them lighter one contains the desired ball. now again take the individual ball and weighs two of them if machine is balanced and lighter one in third ball else you got the desired ball. :)context