Difference between revisions of "2004 Indonesia MO Problems/Problem 8"

(Problem 8)
(Solution)
 
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==Solution==
 
==Solution==
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Let the first 3 rugs occupy the entire floor, then the next rug that you add in, by the pigeon hole principle, it must overlap with another rug. Let a, b and c be the overlapping region with rug 1, rug 2 and rug 3 respectively, a+b+c = 1, thus at least one of a, b and c must be greater than 0.2.

Latest revision as of 03:45, 16 June 2024

Problem 8

A floor with an area of $3 \text{ m}^2$ will be covered by $5$ rugs with various shapes, each having an area of $1 \text{ m}^2$. Show that there exist $2$ overlapping rugs with the overlapped area at least $1/5 \text{ m}^2$.

Solution

Let the first 3 rugs occupy the entire floor, then the next rug that you add in, by the pigeon hole principle, it must overlap with another rug. Let a, b and c be the overlapping region with rug 1, rug 2 and rug 3 respectively, a+b+c = 1, thus at least one of a, b and c must be greater than 0.2.