Make a round-trip of length not divisible by 3
Source: PAMO 2007 Q3
December 10, 2013
geometry3D geometrycombinatorics unsolvedcombinatorics
Problem Statement
In a country, towns are connected by roads. Each town is directly connected to exactly three other towns. Show that there exists a town from which you can make a round-trip, without using the same road more than once, and for which the number of roads used is not divisible by . (Not all towns need to be visited.)