I have posted a similar puzzle before, but no one figured it out. I am reposting an easier version that is 100% independent of the previous one.

Scotland Yard is trying to catch an important London drug cartel. They tend to do large trades worth more than 1 million great British pounds in several locations around London - mainly parks and cemeteries.

Through a network of informers the police have been able to map all the locations where they meet - and you can assume that drug dealers only meet at these locations.

enter image description here

And here is a link for the map with the location names.

The chief of Scotland Yard has assigned a very limited budget to catch this cartel. So each day they can dispatch, at most, a single Anti-Drug unit.

The problem with catching these guys is that the cops do not know, ex-ante, at which place they are planning to meet. Usually a message between buyers and sellers is sent before the next meet. During the past year, cops have managed to intercept few messages, but the messages only contain the time of the next meet and never the location. Out of the messages they have intercepted, some of them Scotland Yard, managed to trace to a location by randomly choosing a location to go. Here are the messages traced which cops have managed to find the meeting location (through the informers network):

enter image description here

The meetings always occur within a 24-hour window from the time the message is intercepted and always occur at the time settled on in the message.

Now the Scotland Yard, decided to hire a consultant, YOU! Today (26-Mar-2018) they have just intercepted this message: " Meet at 9 p.m."

Can you determine where in London the meeting will occur?

Here is the CSV format:

Meeting date,Message,Location

2017-01-03,Meet at 4pm, London zoo
2017-01-11,Meet at 1am, Ruskin Park
2017-01-17,Meet at 7am, Figge's Marsh
2017-01-28,Meet at 3pm, Primrose Hill
2017-02-04,Meet at 2am, Greendale Playing Fields
2017-02-10,Meet at 8pm, Wormwood Park
2017-02-19,Meet at 2am, Greendale Playing Fields
2017-03-03,Meet at 1am, Ruskin Park
2017-03-09,Meet at 8am, Fishponds Playing Field
2017-03-10,Meet at 6am, Croydon Cemetery
2017-03-15,Meet at 2pm, Talacre Gardens

1 Answer 1


Roundwood Park. Each loop contains twelve locations, with the northernmost location designated as 12, and counting clockwise around the clock. The more northern loop is for the PM times, the southern loop for the AM times. Therefore, a meet at 9pm is for the ninth location on the northern loop, which, following the link, is Roundwood Park.

  • $\begingroup$ That's correct. I guess I simplified it too much :) $\endgroup$
    – phdstudent
    Commented Mar 26, 2018 at 13:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.