OK, let us go on a little trip….

The Wiseman Steamship Company has a great reputation for punctual sailings.  Every day at noon (Greenwich time) one of its ships leaves Southampton for New York.  At exactly the same moment another ship leaves New York for Southampton.  The crossing, in either direction, takes seven days and follows the same course.  So, whenever a ship leaves either Southampton or New York, another ship is just docking there having arrived from the opposite direction.

You are lucky enough to get a ticket to travel Southampton to New York, how many Wiseman ships will you meet during your voyage to New York?

As ever, please do NOT post your answers, but do say if you think you have solved the puzzle and how long it took.  Solution on Monday.

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.



  1. I reckon I have an answer. I decided to draw it all out, worked out how to do that, then did it, then realised I made an error in judgement and have now arrived at an answer. According to the twitter timestampl, around 10 minutes.
    I think there may be a little bit of leeway depending on what is meant by “met”.

    1. Yup, putting it in a diagram will be quite convincing. The results are easily expressed in algebra after that, and then one can discuss the fencepost issue.

  2. after about a minute I got to two answers. I’m pretty confident, there’s just a little question over what counts as meeting ‘during your voyage’.

  3. If on the same course, you only meet 1: a terrible crash while leaving the port of Southampton.
    I found another answer in about 1 minute which may survive the weekend.

  4. I had a hunch, but thought I’d better check with a diagram. The hunch was wrong, it was more than I’d thought. Then I realized that with some clever thinking I wouldn’t need my diagram – I knewthe answer! – but I finished the diagram just to check.

  5. I spent time drawing it out. Agree with the ambiguity around ‘met’. Assume that, when you leave and the other one docks / you dock and the other one leaves, that counts as met.

  6. It is highly implausible that the ships will leave and dock at precisely the same time. You need to take into consideration weather conditions, tidal flows, wind speed and direction, tonnage weight, Channel traffic, industrial disputes, piracy etc etc.
    I also question whether a daily steamship service is commercially viable in the present economic climate.
    Also in the US the clocks change on November the 6th, whereas in the UK, its on October 30th. What happens to the timetabling in the days between those two dates?
    So, all in all, a pointless excercise and you would be better off working on the two flagpole problem.

  7. Oooh, an interesting one here… More complex than it first appears! I’ve got a good diagram now, fairly sure of the right answer. Probably took me around 30 mins, but most of that was starting up a drawing program and making the image!

  8. There will be a ship arriving at precisely the moment you leave, and another leaving at precisely the moment you arrive. Do you “meet” either of these?

    The concept of relative speed seems to me a quicker way to the solution. Using that, I had the answer, modulo the end conditions (the problem above) within a second.

  9. After a couple of minutes I realised a very important aspect of the matter, and I think I’ve arrived at the correct solution.

    In the department of not so important considerations, the solution may very a bit depending on the interpretation of “meeting a wiseman boat”.

  10. Got the answer in around a minute.

    It definitely helps to draw a quick sketch.

    Of course, it depends on whether or not you are counting the ship that’s arriving at the same moment you are leaving and vice-versa.

    1. in other words, there are three possible solutions, depending on whether you count the ship that’s arriving when you leave southampton, and the ship that’s leaving when you arrive in new york.

      or four, if you count the ship you’re on as one you’ve “met.”

      the puzzle may be easier to visualize if you replace ships on the sea with buses on a highway that leave/arrive precisely every hour, and take 7 hours for the trip.

  11. Methinks I know, but if the ships pass each other to starboard I won’t meet any of the others on the way to NY, I always travel POSH

  12. If the Mississipi steamer sinks, then the answer will be zero … or depend on how far it got. Otherwise, fairly straightforward depending on how you treat the ‘ends’. I am assuming that meeting has to be done at sea …

  13. It took me a little over a week and a pretty substantial steamship investment, but I’m pretty sure I have the right answer.

    1. It can be done in less than two weeks, you just need the steamships delivered to very specific locations–the tips to all those delivery men cost me almost as much as the ships themselves!

      It’s a good thing I’m filthy rich in my hypothetical world.

  14. I’d say the answer depends on whether there are one or two Wiseman ships in the same port at any one time.

    In other words, does the journey take exactly 7 days, in which case a ship arriving in port would be able to wave to the ones departing; or does it take slightly less than 7 days, in which case the ship arriving in port is also the next ship to depart port.

  15. So what’s the minimum number of ships that the Wiseman Steamship Company needs in its fleet in order to maintain a daily schedule?

    1. Very good question!

      It’s a bit easier to solve since it can be done from the perspective of just one port, working out one full cycle time. Not to forget, of course, time at ports.

  16. Drew all ships at start position lettered and all ships at end position lettered. It was then obvious which ships must have been passed and how many and the answer wasn’t what I first guessed. Took about 2 min.

  17. Do you mean the new ship that has just arrived is travelling in the opposite direction to the one leaving? If it’s arriving from the opposite direction then where is it coming from? I am confused. If I take it as ships are just travelling between the two cities on the same route then I have an answer and I can see the trick that is meant to catch people.

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