43 lines between A and B, 29 lines between B and C
Source: 2011 Swedish Mathematical Competition p4
April 30, 2021
combinatorics
Problem Statement
Towns , and are connected with a telecommunications cable. If you for example want to send a message from to is assigned to either a direct line between and , or if necessary, a line via . There are lines between and , including those who go through , and lines between and , including those who go via . How many lines, are there between and (including those who go via )?