Argentina MO 2021 National Level 1 P4
Source:
April 23, 2022
contestscombinatorics
Problem Statement
Martu wants to build a set of cards with the following properties:• Each card has a positive integer on it.
• The number on each card is equal to one of possible numbers.
• If any two cards are taken and added together, it is always possible to find two other cards in the set such that the sum is the same.Determine the fewest number of cards Martu's set can have and give an example for that number.