Numbers 1, 2, 3, ... 2014 are written on
a board.
You are allowed to replace any
two of these numbers by a new number,
which is either the sum or the difference
of these numbers.
Show that after 2013
times performing this operation, the only
number left on the board cannot be zero.
(In reply to
re(2): All things being equal ... (spoiler) by Charlie)
My reading of the problem conditions is that I must replace both selected numbers with the same number, either the sum or difference. If instead the sum replaces one and the difference replaces the other, then I agree with Steve Herman's answer.

Posted by xdog
on 20131212 18:19:21 