Subject: Re: Old-Ball puzzle
Date: Mon, 16 Mar 1998 15:28:41 +0100
From: Abdelilah Elanbari

Hi Alexander,

I liked very much your solution in weight1.html. It's really ingenious!

But I noticed a little miss in the solution you wrote in https://www.cut-the-knot.com/exchange/weighting2.shtml:

In the case 1-1 (1234 and 5678 are even, 9 and a are even) we'll know the deffective ball but without knowing if it's heavy or light.

A proposal is, rather than comparing 9 and a: compare 9a and b1. We may consider two outcomes.

  1. They are even. c is deffective and compring it with a good ball will show if it's heavy or light
  2. 9a is heavier. Compare 9 and a. Two outcomes are possible.
    1. They are even. b is deffective and light
    2. 9 is heavy. 9 is deffective and heavy.

I hope I'm not wrong.. (Please let me know otherwise)

See you,
Abdelilah

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