SOLUTION: You have ten stacks of coins, each stack consisting of ten half-dollars. One entire stack is counterfeit, but you do not know which one. But you do know the weight of a genuine hal

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Question 98283: You have ten stacks of coins, each stack consisting of ten half-dollars. One entire stack is counterfeit, but you do not know which one. But you do know the weight of a genuine half-dollar (10 grams each), and you are also told that each counterfeit coin weighs 1 gram more than it should. You may weigh the coins on a scale. What is the smallest number of weighings necessary to determine which stack is counterfeit?
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
3 DIFFERENT WEIGHING SHOULD DO IT.
5 & 5 FOR THE FIRST WEIGHING. THE HEAVIEST 5 CONTAINS THE BAD STACK.
DIVIDE THIS 5 INTO 2 SETS OF 2 EACH. THE HEAVIEST SIDE CONTAINS THE BAD STACK.
(WORST CASE)
DIVIDE THE HEAVIEST PAIR AND WEIGH THEM INDIVIDUALLY THE HEAVIEST WILL SHOW UP.