Ships That Pass . . .
In the days when people crossed the Atlantic in passenger liners, a ship left London every day at 4.00 p.m. bound for New York, arriving exactly 7 days later.
Every day at the same instant (11.00 a.m. because of the time difference) a ship left New York bound for London, arriving exactly 7 days later.
All ships followed the same route, deviating slightly to avoid collisions when they met.
How many ships from London does each ship sailing from New York encounter during its transatlantic voyage, not counting any that arrive at the dock just as they leave, or leave the dock just as they arrive?