MathDB

10

Part of 2019 Switzerland Team Selection Test

Problems(1)

Different Colors of Balls

Source: Swiss TST 2019 P10

5/12/2020
Let n≥5n \geq 5 be an integer. A shop sells balls in nn different colors. Each of n+1n + 1 children bought three balls with different colors, but no two children bought exactly the same color combination. Show that there are at least two children who bought exactly one ball of the same color.
combinatorics