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nine nickles

 
 
View Profile joezx3
 
Reply Wed 8 Apr, 2009 09:45 pm
Nine nickels and a traditional balance are lying in front of you. All nickels have the same weight except for one counterfeit, which is slightly heavier than the others. What is the minimum number of times you expect to use the balance to guarantee you've found the counterfeit nickel? Please explain the process you would take.

 
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Reply Wed 8 Apr, 2009 10:59 pm
Two times. Here's how to do it.

First, you separate them into 3 piles of 3 nickels and weigh any two piles. If one of the weighed piles is heavier than the other, the counterfeit is in that pile, if they balance, then your nickel is in the remaining pile. Next you pick two coins from the pile you have identified as the one containing the counterfeit and weigh them. If one is heavier you have your culprit, if they balance the remaining coin from the pile is the counterfeit.
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Reply Thu 9 Apr, 2009 01:51 am
joezx3 wrote:

Quote:
Nine nickels and a traditional balance are lying in front of you.
All nickels have the same weight except for one counterfeit,
which is slightly heavier than the others. What is the minimum
number of times you expect to use the balance to guarantee
you've found the counterfeit nickel?

Please explain the process you would take.


The process I woud take is to go on about my business.
I do not accept nickels nor pennies.





David
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