• PraveenKumar

MemberDec 18, 2011

## 100 Coins!

There are 10 sets of 10 coins. You know how much the coins should weigh. You know all the coins in one set of ten are exactly a hundredth of an ounce off, making the entire set of ten coins a tenth of an ounce off. You also know that all the other coins weight the correct amount. You are allowed to use an extremely accurate digital weighing machine only once.

How do you determine which set of 10 coins is faulty?
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Replies
• MemberDec 20, 2011

Take one coin from the first set, two from the second set and so on.. and all ten from the tenth set.

Weigh them. The expected weight should be 55X, where X is the weight of one coin. If the actual weight is one ounce less than 55X,
then the first set is faulty. If it's two ounces less, then second set is faulty and so on.
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• MemberDec 20, 2011

@SS: Perfect! 😁 Hope you didn't Google! 😛
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• MemberDec 20, 2011

@SS: The same questions was asked by AKD in puzzle thread. Isnt it?
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• MemberDec 20, 2011