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 One of Sixteen (Posted on 2015-12-29)
I have two sets of 8 coins. In one set the coins weigh 30g each, in the other set the coins weigh 31g each.
Unfortunately they got mixed together in one big pile of 16 coins. I want to identify one coin. It can be from either set.

(Easy) Using a balance scale, identify a coin in four weighings.

(Hard) Identify a coin in just three weighings.

 See The Solution Submitted by Brian Smith Rating: 4.0000 (3 votes)

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 re: Solution (hard) | Comment 3 of 12 |
(In reply to Solution (hard) by Paul)

It's more interesting if 1+2 = 3+4. In this case as the 2nd weighing, compare 1+2+3+4 to 5+6+7+8, knowing that all four of the left coins are identical (but not whether they're light or heavy.)

WRONG    what if  both  1+2   and 3+4  weigh 61 g

the rest is wrong as well

 Posted by Ady TZIDON on 2015-12-30 17:01:14

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