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Topic: The Postman
Message: Posted by: alekz (Apr 13, 2004 05:58AM)
Okay, I have to translate this one, so sorry for any mistakes. Hope you'll enjoy it anyway.

There's a man working at a post office. One day he gets four parcels and four adress stickers. Awkward as he is, he mixes the adress stickers, so he doesn't know which one belongs to which parcel. He now puts them randomly on the four parcels and dispatches them.

What is the possibility of exactly 3 parcels going to the right destination?
Message: Posted by: Kevin Ridgeway (Apr 13, 2004 10:20AM)
Impossible

Assuming that each address sticker is for a DIFFERENT address. Then it is impossible for just 3 parcels to be delivered to the correct locations, because that would leave the fourth having no where to go but to the final and correct location.
Message: Posted by: 0pus (Apr 13, 2004 02:11PM)
Same answer, even if there are duplicated addresses.

0pus
Message: Posted by: landmark (Apr 13, 2004 03:07PM)
Nice addition, Opus!

Jack Shalom
Message: Posted by: Samuel Catoe (Apr 13, 2004 07:12PM)
If the address stickers are for the same address, then all four would be sent to the correct address so the answer is still: zero.
Message: Posted by: Jonathan Townsend (Apr 13, 2004 07:36PM)
If the guy were not only clumsy but had dirty hands, it is possible for one or more labels to get smudged. ;)
Message: Posted by: Kevin Ridgeway (Apr 13, 2004 08:34PM)
Opus...Same answer, even if there are duplicated addresses.

You're right, I did'nt quite think the whole thing thru.
Thanks for the extra bit.
Message: Posted by: landmark (Apr 13, 2004 10:04PM)
Okay. And the probability of exactly two envelopes being correctly addressed of the four . . .

Jack
Message: Posted by: Nir Dahan (Apr 14, 2004 02:23AM)
Reminds me of the old challange to try to complete only 5 sides of a rubic's cube...
Message: Posted by: Samuel Catoe (Apr 14, 2004 02:42AM)
I know someone who actually did that. He peeled the sticker off of one side of the puzzle.
Message: Posted by: pxs (Apr 14, 2004 04:50AM)
[quote]
On 2004-04-13 23:04, landmark wrote:
Okay. And the probability of exactly two envelopes being correctly addressed of the four . . .

Jack
[/quote]

1/4, I think
Message: Posted by: alekz (Apr 14, 2004 06:54AM)
[quote]
On 2004-04-13 23:04, landmark wrote:
Okay. And the probability of exactly two envelopes being correctly addressed of the four . . .

Jack
[/quote]

Hmmm.. nCr(4,2)/(4!) = 0.25, iirc.
I hope I remember that correctly. Has been a while since I had it at school.


Okay, another step further:
The probability of a letter being delivered to a wrong adress or not being delivered at all shall be 0.01. NOW what's the probability of exactly 3 letters arriving at the right destination?
Message: Posted by: magicgeorge (Apr 14, 2004 08:48AM)
(1/4 x 1/3 X 1/2) + .04 - ( all the different chances of 2, 3 or 4 not being delivered which I'm too lazy to work out since it's very small anyhow)
Message: Posted by: MacGyver (Apr 14, 2004 09:34AM)
You would have to know the total number of addresses in the world, right?

Because not only would 1 in 10,000 times would the letter have ot be delivered to the wrong location, but it would also have to be delivered to a certain adresss out of the total.
Message: Posted by: alekz (Apr 14, 2004 12:05PM)
[quote]
On 2004-04-14 10:34, MacGyver wrote:
You would have to know the total number of addresses in the world, right?

Because not only would 1 in 10,000 times would the letter have ot be delivered to the wrong location, but it would also have to be delivered to a certain adresss out of the total.
[/quote]

Huh? Isn't it 1 in 100 times?
And the adress to which it goes does not matter, as it is the wrong destination anyway, which is the only thing that counts.

Or am I somehow confused?
Message: Posted by: MacGyver (Apr 15, 2004 12:33PM)
Ok, my post was in reference to the "getting delivered to the wrong location" post.


The only way for 3 packages to get to the right location, would be either all four were rightly addressed and one got shipped to the wrong place, or(and this was the thing my post was talking about) two packages were addressed correctly, two were wrong, but one of those two got delivered to the wrong address, but miraculasly got delivered to it's TRUE address.


So you would be left with these possbilities:

2 Correct, 2 Wrong, then .005% of the time one of the wrong ones also divided by the total number of addresses in the world to figure out the probability of it arriving at the correct address even though it was addressed wrong.

or

All 4 correct, then you have a .01% chance of it being lost or delievered to the wrong location, also yielding 3 correct packages.
Message: Posted by: alekz (Apr 16, 2004 03:48AM)
[quote]
On 2004-04-15 13:33, MacGyver wrote:

[...] or(and this was the thing my post was talking about) two packages were addressed correctly, two were wrong, but one of those two got delivered to the wrong address, but miraculasly got delivered to it's TRUE address.

[/quote]

Woo-Hoo! Now that's cool. I would have never thought of that :)
Message: Posted by: cfleming (Apr 28, 2004 11:31PM)
I work for the post office and know that the first parcel gets missent, the second gets smashed, the third gets returned to sender! The voice of experience!