One on urns
Source: India RMO 1991 Problem 4
October 15, 2005
Problem Statement
There are two urns each containing an arbitrary number of balls. We are allowed two types of operations:
(a) remove an equal number of balls simultaneously from both the urns,
(b) double the number of balls in any of them
Show that after performing these operations finitely many times, both the urns can be made empty.