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Forums > Social Chat > A Good Thing and two goats

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joe_sixsteps


joe_sixsteps

mULti-torTOISe
Location: Kent currently, Cornwall soon,...

Total posts: 310
Posted:Those of you who would appreciate this question have probably heard it already, but here it is again anyway:

You're through to the final round of a gameshow, and the gameshow host has shown you three doors. Behind one of these doors is the grand prize - a Very Good Thing. Like a magic carpet. Behind the other two doors lurk goats, which for the sake of this argument are Not Good Things.

So, you choose your door, but before you open it the host stops you, and opens one of the other doors to show you a goat.

Should you change doors?


(Just to restate the question unnecessarily: at this point you are now standing in front of an unopened door. There is one other door that hasn't been opened. Should you change to the other unopened door, or stick with your first choice, or does it even matter?)

First correct answer that includes a rationale wins a small prize. Like a picture of a fish.


The Confusion Squid has many tentacles

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telic


I don't want a title.


Total posts: 940
Posted:All right, here's another puzzle:

You have a box of matches and two uneven ropes. Each rope takes precisely one hour to burn. Measure out exactly forty-five minutes.

(Note: Folding the ropes won't work, because they're uneven and it might take 20 minutes to burn through one inch and 2 minutes to burn through the next, or whatnot.)


E pluribus unum, baby.

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Doc Lightning
GOLD Member since May 2001

Doc Lightning

HOP Mad Doctor
Location: San Francisco, CA, USA

Total posts: 13920
Posted:Ok. Try this: Light one rope at both ends and the other rope at one end. When the one that's lit at both ends burns out completely, light the other end of the second rope. That's 30 minutes plus 15 minutes.

Did I win a picture of a fish? Huh? Huh? Huh? Did I? Did I?


-Mike )'(
Certified Mad Doctor and HoP High Priest of Nutella

"A buckuht 'n a hooze!" -Valura

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joe_sixsteps


joe_sixsteps

mULti-torTOISe
Location: Kent currently, Cornwall soon,...

Total posts: 310
Posted:Woah, hold on there. Pictures of fish were only being awarded for the goat question I'm afraid... you'll have to apply to regyt for a suitable prize for this one...

The Confusion Squid has many tentacles

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telic


I don't want a title.


Total posts: 940
Posted:Yay, Lghtnng! You win a picture of a miniature donkey:


Non-Https Image Link


[Disclaimer: I'm just a leeeeetle bit obsessed with these things. I want one!]


E pluribus unum, baby.

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polythene


veteran
Location: London/ Surrey

Total posts: 1359
Posted:these made me laugh.....

http://www-personal.umich.edu/~jimknapp/goats.html


The optimist claims that we are living in the best of all possible worlds.
The pessimist fears this is true.

Always make time to play in the snow.

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telic


I don't want a title.


Total posts: 940
Posted:I can't bear the thought of this thread dying, so here's another brainteaser:

There is a barn with no windows. Inside the barn are three lightbulbs. You are outside barn. There are three switches on the outside of the barn. Each switch corresponds to one of the lightbulbs.

Given that the lightbulbs all start off unlit, and you can only go inside the barn once, how can you figure out which switch goes with which bulb?


E pluribus unum, baby.

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Sir_Sheep


Sir_Sheep

old hand
Location: Chester, UK

Total posts: 725
Posted:Leave one switch alone. Switch aother one on. The last switch on, wait for 10 minutes, then switch it off again.

Go inside the barn.

The switch you left alone will still be unlit.
The one you switched on will be lit.
The one you left for 10 minutes will be unlit, but the bulb will be warm.

Ta-dah.

What do I win?


Spoiling Christmas for small children since 2003.

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telic


I don't want a title.


Total posts: 940
Posted:Sir_Sheep, you win an all-expenses-paid trip to the one and only.... your home town!

E pluribus unum, baby.

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Sir_Sheep


Sir_Sheep

old hand
Location: Chester, UK

Total posts: 725
Posted:Bugger that.

You ever been to Cleethorpes?

EXACTLY!


Spoiling Christmas for small children since 2003.

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telic


I don't want a title.


Total posts: 940
Posted:

I don't suppose I could satisfy you with miniature livestock, too? Or cartoony super-deformed groupies? Possibly a limerick?

Anyways, someone needs to post another puzzle!

Do any of you guys do cryptic crosswords? (Instead of trivia, each clue is part definition and part wordplay.)


E pluribus unum, baby.

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Sir_Sheep


Sir_Sheep

old hand
Location: Chester, UK

Total posts: 725
Posted:Miniture livestock all the way hehe

Spoiling Christmas for small children since 2003.

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borismcnorris


borismcnorris

professional pedant
Location: Bristol

Total posts: 137
Posted:A riddle for every one:

What is greater than god and more evil than the devil, rich men want it, poor men have it, and if you eat it you die.

hehe, good luck. I was told that some researchers asked this to a group of 5/6 year olds and a group of Harvard students. The Harvard people took about three hours to get it but the little kids got it almost straight away.


A warrior always returns to the fray. He never does so out of stubbornness, but because he has noticed a change in the weather - Paulo Coelho

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Dunc
GOLD Member since Aug 2003

Dunc

playing the days away
Location: The Middle lands

Total posts: 7263
Posted:quote:Originally posted by regyt:
There are 3 doors, A, B and C. The probability of the winner being door A (the one you're in front of) is 1/3. The probability of the winner being [door B or door C] is 2/3. If you learn that door C is not the winner, the probability of the winner being [door B or door C] remains 2/3.

Ergo, if you switch doors, your chances of winning go from 1/3 to 2/3.
Ok so maybe I'm a little thick but Math was always my strong point...

The probability of door A being the winner is 1/3 yeah...so doesn't that means all doors are 1/3? doors, 1 chance.....3 x 1 = 3
How can door B & C start with a probability of 2/3? It only changes to 2/3 if you know what's behind one door...but if you know what's behind one door you only have two choices left....ergo leaving 1/2 chance each. The open door is no longer part of the equation thus the parts have reduced so the odds must be reduced comparitavily.....

*rushes off to test with friends and cups*


Let's relight this forum ubblove

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telic


I don't want a title.


Total posts: 940
Posted:quote:Originally posted by Custom Bug:
The probability of door A being the winner is 1/3 yeah...so doesn't that means all doors are 1/3? doors, 1 chance.....3 x 1 = 3
How can door B & C start with a probability of 2/3? Because there are three doors and, as you said, each door has a 1/3 chance of being the winner. So door A has 1/3, door B has 1/3, and door C has 1/3. I group them into door A and [door B or door C]. Door A alone is 1/3. [Door B or door C] is 2/3 because the probability of something in that grouping being the winner is equal to the sum of the probabilities of each of the choices in that grouping being the winner.

quote:Originally posted by Custom Bug:
It only changes to 2/3 if you know what's behind one door...but if you know what's behind one door you only have two choices left....ergo leaving 1/2 chance each. The open door is no longer part of the equation thus the parts have reduced so the odds must be reduced comparitavily..... I think that's the illusion of the puzzle. It looks like it switched from 3 doors to 2, so the probability changed. But really, all 3 doors were there when you made your decision, so the only thing that has changed was your knowledge.

You have a 1/3 chance of being right with door A. But say you want to switch... there's a 1/3 chance it's door B and a 1/3 chance it's door C and a 2/3 chance that it's one of them. So, think of it as going for the 2/3 chance over the 1/3 chance and pick [door B or door C]. And then you remember that you've been told it's not door C, so once you've picked that group, you can zero in on the only part of that group it could possibly be, and pick door B. That's how the 2/3 probability gets folded into the other door and why you want to switch.


E pluribus unum, baby.

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Matthew B-M


Matthew B-M

Lemon-Aware Devilstick-wielding Operative
Location: East London Wilds

Total posts: 605
Posted:*mutter* bayesian probability *mutter*

Luv 'n' Lemons
purity :: clarity :: balance

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joe_sixsteps


joe_sixsteps

mULti-torTOISe
Location: Kent currently, Cornwall soon,...

Total posts: 310
Posted:I sent this reply in a PM to someone, but I think it is quite good so I'll post it here as well. Imagine, if you will, that there are in fact a thousand doors. There is still only one Good Thing, but there is now an army of goats. Yuk.

Given a choice of a thousand doors, you are now almost certain to pick a goat. The gameshow host then opens every other door but one, showing you goats each time. You may have picked the car in the first place (one in a thousand chance), and the door he left unopened has an ugly, lice-ridden mangy evil rancid old goat behind it. But it's not very likely. In fact, in nine hundred and ninety nine cases out of a thousand, if you change doors, you get the Good Thing.

However, at the point when there are two doors left, one Good Thing and one poxy goat, you might think that you had a fifty / fifty. And if that didn't get your goat, I can't imagine what would.


The Confusion Squid has many tentacles

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onewheeldave
GOLD Member since Aug 2002

Carpal \'Tunnel
Location: sheffield

Total posts: 3252
Posted:quote:Originally posted by borismcnorris:
A riddle for every one:

What is greater than god and more evil than the devil, rich men want it, poor men have it, and if you eat it you die.

Nothing?


"You can't outrun Death forever.
But you can make the Bastard work for it."

--MAJOR KORGO KORGAR,
"Last of The Lancers"
AFC 32


Educate your self in the Hazards of Fire Breathing STAY SAFE!

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telic


I don't want a title.


Total posts: 940
Posted:::imagines what she could do with an army of goats::

E pluribus unum, baby.

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joe_sixsteps


joe_sixsteps

mULti-torTOISe
Location: Kent currently, Cornwall soon,...

Total posts: 310
Posted:::tries not to imagine regyt doing anything with an army of goats::

The Confusion Squid has many tentacles

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