min time for 4 people to pass a dark tunnel, one torch, at most 2
Source: 2002 Estonia National Olympiad Final Round grade 12 p1
March 14, 2020
algebramin
Problem Statement
Peeter, Juri, Kati and Mari are standing at the entrance of a dark tunnel. They have one torch and none of them dares to be in the tunnel without it, but the tunnel is so narrow that at most two people can move together. It takes minute for Peeter, minutes for Juri, for Kati and for Mari to pass the tunnel. Find the minimum time in which they can all pass through the tunnel.