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wonderful
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 Coin weghting: 13 coins with  2 defected coins   « on: Apr 3rd, 2008, 4:45pm » Quote Modify

I posted the same question in the "easy" section a a follow-up 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 (A-2) g.

Can you find out the two different coins using minimum weightings?

Have A Great Day!
 « Last Edit: Apr 3rd, 2008, 7:23pm by wonderful » IP Logged
Grimbal
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 Re: Coin weghting: 13 coins with  2 defected   « Reply #1 on: Apr 4th, 2008, 6:00am » Quote Modify

Are these weightings on a 2-pan scale or on a scale that gives the weight?
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Hippo
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 Re: Coin weghting: 13 coins with  2 defected   « Reply #2 on: Apr 4th, 2008, 1:11pm » Quote Modify

I expect its the same puzzle with 8 replaced by 13, so the 2pan scales are expected.

So for the start there is 34<13*12<35 initial positions so we are trying to find solution on 5 measurements.
 « Last Edit: Apr 4th, 2008, 1:11pm by Hippo » IP Logged
wonderful
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 Re: Coin weghting: 13 coins with  2 defected coins   « Reply #3 on: Apr 4th, 2008, 9:14pm » Quote Modify

5 is the correct answer. Next, we would like to design a weighting scheme to achieve this target. Result from the 8 coins can be used here.

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wonderful
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 Re: Coin weghting: 13 coins with  2 defected coins   « Reply #4 on: Apr 14th, 2008, 2:31am » Quote Modify

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:

In the first three weighting we can do something like this:

(5, 6, 7,  ?  (9,10,11,12)
(2, 8, 11, 12) ?  (3, 4, 9, 10)
(1, 4, 6, 10) ? (3, 7, 9, 12)

After that, there are two more weightings.
Let's continue.

Have A Great Day!
 « Last Edit: Apr 14th, 2008, 2:34am by wonderful » IP Logged
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