perplexus.info :: Weights and Scales : Take the right one

Take the right one (Posted on 2013-10-18)

Among 100 coins exactly 4 are fake. All genuine coins weigh the same; all fake coins, too. A fake coin is lighter than a genuine coin.

How would we find at least one genuine coin using two weighings on a balance scale?

Source: 2010 Euler math Olympiad in Russia- authored by A.Shapovalov

No Solution Yet Submitted by Ady TZIDON

Rating: 3.0000 (1 votes)

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re: Query .....answered

Comment 18 of 18 |

(In reply to Query by Kenny M)

The heavy part has at most 1 fake (light) coin.

Pick two coins from the heavier side and compare them ()2nd weighing).

If they balance they're both normal, otherwise the heavier is normal.

See other posts, - for "=" case.

Posted by Ady TZIDON on 2013-10-26 05:06:23

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