olymmath

FI-MO 2008

Finnish national mathematics olympiad 2008.

Other problems

Problem 1

Foxes, wolves and bears arranged a big rabbit hunt. There were 4545 hunters catching 20082008 rabbits. Every fox caught 5959 rabbits, every wolf 4141 rabbits and every bear 4040 rabbits. How many foxes, wolves and bears were there in the hunting company?

Problem 2

The incentre of the triangle ABCABC is I.I. The lines AI,BIAI, BI and CICI meet the circumcircle of the triangle ABCABC also at points D,ED, E and F,F, respectively. Prove that ADAD and EFEF are perpendicular.

Problem 3

Solve the diophantine equation x2008−y2008=22009.x^{2008}- y^{2008} = 2^{2009}.

Problem 4

Eight football teams play matches against each other in such a way that no two teams meet twice and no three teams play all of the three possible matches. What is the largest possible number of matches?

Problem 5

The closed line segment II is covered by finitely many closed line segments. Show that one can choose a subfamily SS of the family of line segments having the properties: (1) the chosen line segments are disjoint, (2) the sum of the lengths of the line segments of S is more than half of the length of I.I. Show that the claim does not hold any more if the line segment II is replaced by a circle and other occurences of the compound word ''line segment" by the word ''circular arc".