MathDB
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 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".