52nd Kürschák Competition 1951

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1.  ABCD is a square. E is a point on the side BC such that BE = BC/3, and F is a point on the ray DC such that CF = DC/2. Prove that the lines AE and BF intersect on the circumcircle of the square.

2.  For which m > 1 is (m-1)! divisible by m?
3.  An open half-plane is the set of all points lying to one side of a line, but excluding the points on the line itself. If four open half-planes cover the plane, show that one can select three of them which still cover the plane.

The original problems are in Hungarian. Many thanks to Péter Dombi for the translation.

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(C) John Scholes
jscholes@kalva.demon.co.uk
19 Apr 2003
Last corrected/updated 19 Apr 2003