smallest number at least 3 cards have equal sums of digits (100-999)
Source: 1999 Spanish Mathematical Olympiad P4
July 21, 2018
number theorysum of digitsminimum
Problem Statement
A box contains cards, labeled from to . Cards are removed one at a time without replacement. What is the smallest number of cards that must be removed to guarantee that the labels of at least three removed cards have equal sums of digits?