James, I'm going to duck your question, and let Henry decide how to answer, if to answer at all. -tom On Mon, May 9, 2016 at 10:31 AM, James Propp <jamespropp@gmail.com> wrote:
I'm unclear on the meaning of "unless the post office believes a key to that box will eventually be". What are the laws of belief? If I write a letter saying "I'm never going to send the key because you already have it," might the post office believe me? I could then break my word and send a key after all. Does the puzzle require that the post office never believes something that turns out to be wrong?
Jim
On Monday, May 9, 2016, Tom Rokicki <rokicki@gmail.com> wrote:
A locked box containing a key to some other box will get through (unless the post office believes a key to that box will eventually be sent).
You can assume a key send will not get through (or rather, that the postal system will retain a copy of any key sent through).
There is a good solution that doesn't require any special tricks (landscapes or otherwise). The problem statement sets the parameters in a reasonable fashion; don't try to work around the parameters but instead look for a solution to the problem.
-tom
On Mon, May 9, 2016 at 10:12 AM, Joerg Arndt <arndt@jjj.de <javascript:;>> wrote:
Will a locked box containing a key to some other box get through? Will a key send (before the corresponding box is send) get through?
Best regards, jj
* Henry Baker <hbaker1@pipeline.com <javascript:;>> [May 09. 2016 16:23]:
I don't recall if this problem was ever discussed on math-fun: --- The Russian Postal Service Problem
A man in the west of Russia wants to send a small but expensive gift (a ring) to his lady love who lives in the east. Unfortunately, the Russian postal service is corrupt: they will open every letter they get and remove any valuables from them before sending them on.
The man could send the ring in a locked box (the postal service is underfunded and cannot afford tools to break into locked boxes), but his partner would have no way of opening the box. If the postal service believe he will send a key separately, they will hold onto the box until the key arrives.
He could use a combination lock and telephone the combination to her, but the KGB monitor all phone lines and will tell their mates in the postal service everything he says. He can still talk to her; he just can't rely on secrecy.
So, the postal service will deliver the parcel intact only if it is locked and if they know that no key will ever come their way. Delivering the ring in person is not an option.
How does he safely send the ring to his partner?
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