Latest Wipro Aptitude Question SOLUTION: Out of 80 coins, one is counterfeit. What is the minimum number of weighings needed to find out the counterfeit coin?

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Out of 80 coins, one is counterfeit. What is the minimum number of weighings needed to find out the counterfeit coin?

Asked In Wipro (12 years ago)

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Read Solution (3) :

Shiv Kumar  (12 years ago)

The answer is 4 weighings

Start by dividing the pile into 3 groups (27,27,27).

Weigh two of the groups. If one side goes up, it contains the light, counterfeit coin. If they balance, it is in the unweighed group.

Now repeat the process with the group of 27 you have found. This time divide it into 9,9,9.

Once you have figured out the group of 9, divide it into 3,3,3 and repeat the process.

Finally divide it into 1,1,1. The final (4th) weighing will discover the counterfeit coin.

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vsk  (12 years ago)

80-1=79
after that i dnt know

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Dr.Dipin Singh  (12 years ago)

It is possible in 4 weighings only if we know whether the counterfeit coin is heavier or lighter than other 79 coins.

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