Start - end by turning left and right alternatively, why?

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SUMMARY

The discussion focuses on a mathematical proof regarding a network of villages where each village is connected by three roads. The key conclusion is that if a person starts at one village and alternates turning left and right at each village, they will eventually return to the starting point. The proof hinges on the structure of the road system and the parity of the number of villages, specifically that the process is guaranteed to work with an even number of villages. The reasoning involves analyzing the movement patterns and the cyclical nature of the turns.

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  • Understanding of graph theory, specifically Eulerian paths.
  • Familiarity with basic concepts of topology.
  • Knowledge of parity in mathematics, particularly even and odd numbers.
  • Ability to construct logical proofs in mathematics.
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This discussion is beneficial for mathematicians, students studying graph theory, and anyone interested in mathematical proofs related to movement in networks.

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Homework Statement



In a certain area there are n villages linked by a network of roads
in such a way that exactly three roads meet in each village,
and none of the roads meet between villages. Prove that if
someone starts in one village and moves round this road system
alternately turning right and left whenever he comes to a village,
then he will eventually return to the village he started from

Homework Equations





The Attempt at a Solution

 
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i assume this only works if the number of villages is even. Let i=1,2,... then when we have 2i villages we have 3i roads. I can see that when you go alternatively left and right you end up at the start point, I am just not sure why/ can't prove it.
 

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