perplexus.info :: Weights and Scales : True coins, fake coins

True coins, fake coins (Posted on 2008-10-23)

You have eight bags, each of them containing 48 coins.

Five of these bags contain only true coins, the rest of them contain fake coins. Fake coins weigh 1 gram less than the real coins.

You do not know what bags have fake coins and what bags have real coins. You do not know also, besides that it is an integer value, the weight of the real coins.

You can use a digital or analog reading scale with precision up to 1 gram.

Making only one weighing and using the minimum number of coins, how can you find the bags containing the fake coins?

Submitted by pcbouhid

Rating: 5.0000 (1 votes)

Solution: (Hide)

Take out 0 (no coin from the first bag), 1 (one coin from the second bag etc.), 2, 4, 7, 13, 24, 44 coins (from the last 8th bag). Each triple is unique enabling an easy way to identify the bags with fake coins (using only 95 coins).

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Oops	joe	2013-02-28 13:13:25
re: really?	Charlie	2013-02-27 14:24:32
really?	joe	2013-02-27 12:23:28
re(2): better -- within the constraints of the puzzle	Charlie	2008-10-24 01:57:08
re: Looking for an answer	Steve Herman	2008-10-23 23:32:06
Looking for an answer	Leming	2008-10-23 19:34:50
re: better -- within the constraints of the puzzle	rod hines	2008-10-23 16:42:56
better -- within the constraints of the puzzle	Charlie	2008-10-23 15:57:17
not quite -- my best	Charlie	2008-10-23 13:35:52

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