perplexus.info :: Weights and Scales : Many coins

Many coins - one fake (Posted on 2003-05-14)

Given a balance scale that is sure to break after X weighings, find an equation for the largest number of coins N, from which you can determine a fake coin that has the wrong weight if

A: You know whether the fake is lighter or heavier

B: You do not know whether the fake is lighter or heavier

(Assume only one of the N coins is fake)

Submitted by Jonathan Waltz

Rating: 3.7143 (7 votes)

Solution: (Hide)

Pleasance offers solutions here and expands on the second part here.
Also of interest is this post by Sanjay

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

Subject	Author	Date
Solution	FrankM	2008-02-16 13:07:19
my solution	geoffrey	2003-10-09 14:53:17
re: solution to B	John Smith	2003-09-03 16:00:26
re(3): solution to B - apologies	Sanjay	2003-05-19 09:00:57
re(4): solution to B	pleasance	2003-05-19 06:49:49
re(3): solution to B	Charlie	2003-05-19 04:30:47
re(2): solution to B	pleasance	2003-05-19 03:18:05
re: solution to B	Sanjay	2003-05-18 10:12:28
re: solution to B	Charlie	2003-05-18 04:48:18
solution to B	pleasance	2003-05-18 01:55:49
The answer to 'fakeness'	Sanjay	2003-05-16 16:31:42
another approach to problem B	pleasance	2003-05-16 02:35:00
re(4): Weighty Solution (maybe!)	Chris	2003-05-15 06:53:29
re(3): Weighty Solution (maybe!)	Chris	2003-05-15 06:43:16
re(3): Weighty Solution (maybe!)	Hank	2003-05-15 03:07:01
re(2): Weighty Solution (maybe!)	Gamer	2003-05-14 12:22:35
re: Weighty Solution (maybe!)	Chris	2003-05-14 10:48:06
Weighty Solution (maybe!)	Chris	2003-05-14 10:30:45
Weighing in on this one....	Brian Smith	2003-05-14 09:21:22
solution for A; thoughts on B	Charlie	2003-05-14 09:17:00

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