MathDB
Finding Weights With Errors

Source: KöMaL A. 763

March 20, 2022
combinatoricskomal

Problem Statement

Let k2k\geq 2 be an integer. We want to determine the weight of nn balls. One try consists of choosing two balls, and we are given the sum of the weights of the two chosen balls. We know that at most kk of the answers can be wrong. Let fk(n)f_k(n) denote the smallest number for which it is true that we can always find the weights of the balls with fk(n)f_k(n) tries (the tries don't have to be decided in advance). Prove that there exist numbers aka_k and bkb_k for which fk(n)aknbk|f_k(n)-a_kn|\leq b_k holds.
Proposed by Surányi László, Budapest and Bálint Virág, Toronto