MathDB
JBMO Shortlist 2019 A3

Source:

September 12, 2020
algebra

Problem Statement

Let AA and BB be two non-empty subsets of X={1,2,...,11}X = \{1, 2, . . . , 11 \} with AB=XA \cup B = X. Let PAP_A be the product of all elements of AA and let PBP_B be the product of all elements of BB. Find the minimum and maximum possible value of PA+PBP_A +P_B and find all possible equality cases.
Proposed by Greece