Granny Smith, who was leaving London, boarded a train at four minutes past the hour.
logic/meeting.trains New
New entry, edited from material collected for the archive and not yet in a released version.
Problem
Granny Smith, who was leaving London, boarded a train at four minutes past the hour. After boarding, she stuck her head out of the window and shouted to the ticket man, "How far are we from Edinburgh?" "All trains take five hours either way," he replied. "How many trains shall I meet on the way?" asked Granny. "A train leaves Edinburgh at five minutes past the hour, every hour," answered the ticket man as Granny mumbled about the difficulty of getting a straight answer these days. How many trains will Granny Smith meet on her journey up to Edinburgh? -- Anders Jejje Johanson <jejje@hem.passagen.se>
Show solution
More than you would think. Let's say Granny leaves at 6 o'clock. Then the train she doesn't meet in London is the one that left at 1, and the one she doesn't meet in Edinburgh is the one that leaves at 11, when she gets there. She meets the nine trains in between. -- Jonathan Dushoff <dushoff@gate.sinica.edu.tw> [ Editor: this ignores the minutes in the puzzle. If Granny leaves at 6:04, the train that left Edinburgh at 1:05 reaches London at 6:05, one minute after she leaves, so she does meet it on the line. ] 11 trains -- Rama Rao Kotapally <rrk2f@virginia.edu> I'm not convinced ! -- Anders Jejje Johanson <jejje@hem.passagen.se>