MathDB

5

Part of 2022 Dutch BxMO TST

Problems(1)

Fisherman and some kinds of fish

Source: Turkey 2021 IMO TST Problem 4

5/23/2021
In a fish shop with 28 kinds of fish, there are 28 fish sellers. In every seller, there exists only one type of each fish kind, depending on where it comes, Mediterranean or Black Sea. Each of the kk people gets exactly one fish from each seller and exactly one fish of each kind. For any two people, there exists a fish kind which they have different types of it (one Mediterranean, one Black Sea). What is the maximum possible number of kk?
Turkeycombinatorics