

Title: Coin weghting: 13 coins with 2 defected coins Post by wonderful on Apr 3^{rd}, 2008, 4:45pm I posted the same question in the "easy" section a a followup to Hippo's correct answer for the case of 8 coins. That said, it might be more relevant to post this question here: There are 13 coins of which 11 weighs A g each. The other two are defected. One weighs (A+ 2) g and the other weighs (A2) g. Can you find out the two different coins using minimum weightings? Have A Great Day! 

Title: Re: Coin weghting: 13 coins with 2 defected Post by Grimbal on Apr 4^{th}, 2008, 6:00am Are these weightings on a 2pan scale or on a scale that gives the weight? 

Title: Re: Coin weghting: 13 coins with 2 defected Post by Hippo on Apr 4^{th}, 2008, 1:11pm I expect its the same puzzle with 8 replaced by 13, so the 2pan scales are expected. So for the start there is 3^{4}<13*12<3^{5} initial positions so we are trying to find solution on 5 measurements. 

Title: Re: Coin weghting: 13 coins with 2 defected coins Post by wonderful on Apr 4^{th}, 2008, 9:14pm [hide]5 is the correct answer.[/hide] Next, we would like to design a weighting scheme to achieve this target. Result from the 8 coins can be used here. Have A Great Day! 

Title: Re: Coin weghting: 13 coins with 2 defected coins Post by wonderful on Apr 14^{th}, 2008, 2:31am It has been a while and it seems that nobody has come up with a solution. As such, I would like to give some hints here: [hide]In the first three weighting we can do something like this: (5, 6, 7, 8) ? (9,10,11,12) (2, 8, 11, 12) ? (3, 4, 9, 10) (1, 4, 6, 10) ? (3, 7, 9, 12)[/hide] After that, there are two more weightings. Let's continue. Have A Great Day! 

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