Estonian Math Competitions 2006/2007
Source: Finalround Problem 2
July 29, 2008
combinatorics unsolvedcombinatorics
Problem Statement
Juhan wants to order by weight five balls of pairwise different weight, using only a balance scale. First, he labels the balls with numbers 1 to 5 and creates a list of weighings, such that each element in the list is a pair of two balls. Then, for every pair in the list, he weighs the two balls against each other. Can Juhan sort the balls by weight, using a list with less than 10 pairs?