Reciprocals on blackboard
Source: Pan African MO 2012 Day 2 Q1
October 14, 2012
inductionSFFTgeometry3D geometryinvariantspecial factorizationscombinatorics proposed
Problem Statement
The numbers are written on the blackboard. Aïcha chooses any two numbers from the blackboard, say and , erases them and she writes instead the number . She continues to do this until only one number is left on the board. What are the possible values of the final number?