I was asked to erase one number from a series 3,13,23,…103 and then to erase two members of the remaining sequence, then three and finally four.
I was requested to make sure that after each step of erasures the sum of the remaining members will be divisible by eleven.

Rather than trying to find the "right" order of erasures prove that it cannot be done.

(In reply to solution (spoiler) by xdog)

Your proof was as I would have given it. Well done.

Posted by Dej Mar on 2011-04-19 06:27:47