Covering a line segment with line segments
Source: Finnish Mathematics Competition 2008, Final Round, Problem 5
November 14, 2011
combinatorics unsolvedcombinatorics
Problem Statement
The closed line segment is covered by finitely many closed line segments.
Show that one can choose a subfamily 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 Show that the claim does not hold any more if the line segment is replaced by a circle and other occurences of the compound word ''line segment" by the word ''circular arc".