MathDB
TOT 337 1992 Spring A S5 100 silver and 101 gold coins

Source:

June 9, 2024
weighingscombinatorics

Problem Statement

100100 silver coins ordered by weight and 101101 gold coins also ordered by weight are given. All coins have different weights. You are given a balance to compare weights of any two coins. How can you find the “middle” coin (that occupies the 101101-st place in weight among all 201201 coins) using the minimal number of weighings? Find this number and prove that a smaller number of weighings would be insufficient.
(A. Andjans, Riga)