Question 121
Eleven linguists were instructed to learn eleven foreign languages (initially, none of the linguists knew any of those languages). It became necessary to invite a Foreign Consultant who is able to teach (by means of hypnosis, of course!) any two linguists any two languages during one session (so that each one of those two linguists learns each one of those two languages). What is the minimal number of sessions required to teach all the eleven linguists all the eleven languages (a linguist may attend a session even if he has learnt one of the appropriate languages already)?