7 numbers are drawn out of 55 in the Intergalactic Lottery
Source: 2019 Dürer Math Competition Finals E+1.4
November 28, 2020
combinatorics
Problem Statement
In the Intergalactic Lottery, numbers are drawn out of . R2-D2 and C-3PO decide that they want to win this lottery, so they fill out lottery tickets separately such that for each possible draw one of them does have a winning ticket for that draw. Prove that one of them has tickets with all different numbers.