A senior member of a 100-member society was informed about a certain change regarding the nearest convention and was forced to inform the rest of the members about such change. He calls 3 members and provides each of them with a detailed schedule of a "telephone tree": each of the recipients will call upon 3 new members ,those will address each 3 members and so on until the relevant information is known to each member of the society.

Assuming an optimal efficiency of the method, what is the greatest number of members who need not make a call?

(In reply to solution if there's no trick by Charlie)

....there's no trick

Posted by Ady TZIDON on 2016-07-26 23:37:05