IMO 2024 Shortlist C6
Let n and T be positive integers. James has 4n marbles with weights 1, 2, ..., 4n. He places them on a balance scale, so...
Category: Combinatorics
Problem
Let n and T be positive integers. James has 4n marbles with weights 1, 2, ..., 4n. He places them on a balance scale, so that both sides have equal weight. Andrew may move a marble from one side of the scale to the other, so that the absolute difference in weights of the two sides remains at most T. Find, in terms of n, the minimum positive integer T such that Andrew may make a sequence of moves such that each marble ends up on the opposite side of the scale, regardless of how James initially placed the marbles. (Ghana)