MathDB

2. Each of

n

members of a club is given a different item of information. The members are allowed to share the information, but, for security reasons, only in the following way: A pair may communicate by telephone. During a telephone call only one member may speak. The member who speaks may tell the other member all the information (s)he knows. Determine the minimal number of phone calls that are required to convey all the information to each of the members.
Hi, from my sketches I'm thinking the answer is

2n-2

but I dont know how to prove that this number of calls is the smallest. Can anyone enlighten me? Thanks

Problem Statement