MathDB

30

persons are sitting at round table. 30 \minus{} N of them always speak true ("true speakers") while the other

N

of them sometimes speak true sometimes not ("lie speakers"). Question: "Who is your right neighbour - "true speaker" or "lie speaker" ?" is asked to all 30 persons and 30 answers are collected. What is maximal number

N

for which (with knowledge of these answers) we can always be sure (decide) about at least one person who is "true speaker".

Problem Statement