perplexus.info :: Weights and Scales : One out of ninety

One out of ninety (Posted on 2013-12-17)

You are presented with a set of 90 coins, appearing identical.
Actually, 89 of them are identical, but one has a different weight.
Using balance scales you have to find the odd coin,
paying $10 each time you use the scales.

What is the maximal (i.e. the worst case) cost to accomplish it?

Submitted by Ady TZIDON

Rating: 4.0000 (1 votes)

Solution: (Hide)

$50 (5 weighings) WILL DO.
See all Steve Herman's posts.

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

Subject	Author	Date
One out of 121 !!	Steve Herman	2015-12-19 19:20:20
re: One out of One Hundred Twenty!	Steve Herman	2015-12-18 20:18:01
One out of One Hundred Twenty!	Brian Smith	2015-12-18 00:03:15
One out of 121?	Steve Herman	2013-12-18 22:34:02
One out of 92! (spoiler)	Steve Herman	2013-12-18 12:58:52
Minimum of the minimum of the maximum	Steve Herman	2013-12-17 16:27:22
Where there's a will, there's a weigh (spoiler?)	Steve Herman	2013-12-17 16:02:36

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