2013 UMO Problems/Problem 1

Problem

Consider the following diagram.

$[asy] path S=polygon(4); D(S,black+linewidth(.75)); D(shift(sqrt(2),0)*S,black+linewidth(.75)); D(shift(2*sqrt(2),0)*S,black+linewidth(.75)); D(shift(sqrt(2),sqrt(2))*S,black+linewidth(.75)); D(shift(2*sqrt(2),sqrt(2))*S,black+linewidth(.75)); D(shift(2*sqrt(2),2*sqrt(2))*S,black+linewidth(.75)); [/asy]$

(a) Show that you can retrace the diagram without lifting up your pencil using exactly nine (possibly overlapping) line segments.

(b) Show that you cannot retrace the diagram in the same way using eight or fewer segments.

2013 UMO (Problems • Answer Key • Resources)
Preceded by First Problem	Followed by Problem 2
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2013 UMO Problems/Problem 1

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