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 http://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

Copyright © 1996-2009 Alexander Bogomolny

31176289