olymmath

IR-MO 2008

Iran Mathematical Olympiad 2008.

Other problems

Problem 6

There are five research labs on Mars. Is it always possible to divide Mars to five connected congruent regions such that each region contains exactly on research lab. Image

Problem 7

A graph is called a self-intersectinggraph if it is isomorphic to a graph whose every edge is a segment and every two edges intersect. Notice that no edge contains a vertex except its two endings. a) Find all nn 's for which the cycle of length nn is self-intersecting. b) Prove that in a self-intersecting graph ∣E(G)∣≤∣V(G)∣|E(G)|\leq|V(G)| . c) Find all self-intersecting graphs. Image

Problem 8

In an old script found in ruins of Perspolis is written:


This script has been finished in a year whose 13th power is
258145266804692077858261512663
You should know that if you are skilled in Arithmetics you will know the year this script is finished easily.

Find the year the script is finished. Give a reason for your answer.