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Author Topic:   A test of your common sense
Tangle
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Posts: 5872
From: UK
Joined: 10-07-2011
Member Rating: 2.3


Message 61 of 137 (665855)
06-18-2012 2:19 PM
Reply to: Message 58 by Taz
06-18-2012 2:12 PM


Taz writes:

Unless I'm mistaken, a quick run through in my head says the ball costs 5 cents. But I have a feeling this is not the answer because there's a trick I'm not catching.

Yes, that's correct. It's not a trick or a hard question, but the majority of people asked it will say 10 cents. THAT'S why you can't rely on common sense - people have cognitive bias.

http://en.wikipedia.org/wiki/Cognitive_bias


Life, don't talk to me about life - Marvin the Paranoid Android

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Drosophilla
Member (Idle past 1474 days)
Posts: 172
From: Doncaster, yorkshire, UK
Joined: 08-25-2009


Message 62 of 137 (665857)
06-18-2012 2:21 PM
Reply to: Message 59 by Tangle
06-18-2012 2:13 PM


The surprising answer is that, if you call I have the Ace of Spades, it is more likely that you have another Ace than if you just state I have an Ace!
If you state you have the Ace of Spades there is an 11686 / 20825 chance you have (at least) another Ace, which is 56.12%. If you state you have An Ace then the chance you have (at least) another Ace is 5359 / 14498 (which is 36.27%). Its over 50% less likely!

How come? Well, this puzzle is more about a confidence problem than a probability problem. Its about the disclosure of information.

Clear as mud !!!

I haven't a clue how you worked those percentages out!


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Huntard
Member (Idle past 128 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 63 of 137 (665858)
06-18-2012 2:28 PM
Reply to: Message 54 by Taz
06-18-2012 1:38 PM


You being an ex cop, it makes me wonder why you would say the beam is held up by two insane people....

Regardless, my common sense says the bar will break at the things holding it up (either end, perhaps both, or the things themselves), since those aren't as flexible as the middle part of the bar, where the two people are sitting.

But then again, my "common sense" is mostly pretty fucking shitty, which is why I tend not to rely on it.


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Huntard
Member (Idle past 128 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 64 of 137 (665859)
06-18-2012 2:30 PM
Reply to: Message 59 by Tangle
06-18-2012 2:13 PM


Tangle writes:

Clear? I'm not.


I'm not either. How do you arrive at the 11686 / 20825 and 5359 / 14498 chances?
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Tangle
Member
Posts: 5872
From: UK
Joined: 10-07-2011
Member Rating: 2.3


Message 65 of 137 (665860)
06-18-2012 2:35 PM
Reply to: Message 64 by Huntard
06-18-2012 2:30 PM


Don't shoot the messenger...

First a few basics:

Total_Number_Hands All possible ways to combine the cards to make a Bridge hand. There are 52 cards in a deck, and 13 cards in a hand = b{52,13}

No_Aces The number of hands that have no Aces. There are 48 non-Ace cards, and 13 in a hand = b{48,13}

At_Least_One_Ace The number of hands that have at least one Ace = Total_Number_Hands - No_Aces

Excatly_One_Ace The number of hands that have just one Ace. (Chose any Ace, then choose 12 non-aces) = b{4,1} x b{48,12}

At_Least_Two_Aces Start with the total number of hands, then subtract hands with either no Aces, or one Ace. You are left with the number of hands with two or more Aces = Total_Number_Hands - (No_Aces + Exactly_One_Ace)

We now have enough to calculate our first ratio (chances of having a second Ace if you state you have an Ace):

At_Least_Two_Aces / At_Least_One_Ace = 36.27%

To calculate the ratio where the person claims to have the Ace of Spades, we need some additional terms:

With_Ace_Spades Number of hands with Ace of Spades. (We choose the Ace of Spades, and then have to choose an additional 12 cards from the remaining 51) = b{51,12}

No_Other_Aces Number of hands with no other Aces = b{48,12}

At_Least_Two_Aces_(Including_Ace_Spade) Number of hands with at least two Aces, one of which is the Ace of Spades = With_Ace_Spades - No_Other_Aces

We now have enough to calculate our second ratio (chances of having a second Ace if you state you have the Ace of Spades):

At_Least_Two_Aces_(Including_Ace_Spade) / With_Ace_Spades = 56.12%


Life, don't talk to me about life - Marvin the Paranoid Android

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xongsmith
Member
Posts: 1849
From: massachusetts US
Joined: 01-01-2009


Message 66 of 137 (665862)
06-18-2012 4:14 PM
Reply to: Message 54 by Taz
06-18-2012 1:38 PM


Taz restates his question:

We have a long thing made from a hard material that is designed to only withstand 500 pounds. The long thing is held up at the ends by two 10-96's. 2 insanely overweight women, each weighing 500 pounds, decide to sit on two points L distance from the ends and the women are also L distance from each other.

Where on the long thing will the crack or breaking occur?

This is much better!

My inferior common sense tells me it breaks simultaneously under each woman.

P.S. - what's a 10-96? Is that some kind of cinder block?


- xongsmith, 5.7d

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nwr
Member
Posts: 5579
From: Geneva, Illinois
Joined: 08-08-2005


Message 67 of 137 (665863)
06-18-2012 4:15 PM
Reply to: Message 54 by Taz
06-18-2012 1:38 PM


Taz writes:
We have a long thing made from a hard material that is designed to only withstand 500 pounds.

What does that even mean? What kind of force is that referring to?

If I lay a sheet of fibre board on the ground, it can probably withstand a vertical force of 500 lbs without problem. But if I make a bridge with it, then it will probably fail with smaller forces because those are twisting forces rather than surface pressure.


Jesus was a liberal hippie

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Taz
Member (Idle past 1124 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 68 of 137 (665866)
06-18-2012 5:00 PM
Reply to: Message 66 by xongsmith
06-18-2012 4:14 PM


xongsmith writes:

P.S. - what's a 10-96? Is that some kind of cinder block?


It's cop talk. I used to be a cop. After beating up a few innocent kids and then planted some drugs on them, I decided to change career path.
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xongsmith
Member
Posts: 1849
From: massachusetts US
Joined: 01-01-2009


(1)
Message 69 of 137 (665869)
06-18-2012 10:57 PM
Reply to: Message 68 by Taz
06-18-2012 5:00 PM


Taz replies:
xongsmith writes:

P.S. - what's a 10-96? Is that some kind of cinder block?


It's cop talk.

How do you know the two 10-96's won't immediately drop the long thing upon sight of the two fat women approaching it, run over to them and then start furiously smearing their secret stash of Boysenberry jam all over them, singing "Oh yes, we're going to Heaven now, we're going to Heaven now! Oh yes, we're going to Heaven now!" ?


- xongsmith, 5.7d

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Coyote
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Posts: 6117
Joined: 01-12-2008
Member Rating: 2.0


(1)
Message 70 of 137 (665925)
06-19-2012 8:47 PM
Reply to: Message 1 by Taz
06-16-2012 5:48 PM


How do you...
OK, taz. I have one for you.

How do you keep a turkey in suspense?

(Answer next week. Maybe.)


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RAZD
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Posts: 19525
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.8


(1)
Message 71 of 137 (665926)
06-19-2012 9:05 PM
Reply to: Message 36 by Heathen
06-18-2012 9:10 AM


the technical "language" used ...
Hi Heathen

Just to jump in here.
I'm a structural/stress engineer and deal with this kind of problem regularly.
For clarity (and correct me if I'm wrong here Taz)
The triangle at point A represents a "Simple Support" [edit: a simple support allows rotation but not translation] and the circle at point B represent a support that allows a horizontal translation and prevents vertical translation [edit: and allows rotation].

Indeed, and this is part of your "common knowledge" even though not everyone knows it or understands your explanation ...

This is part of the "technical language" of structural/stress engineering, where the symbols used represent whole phrases and contexts that someone not educated as an engineer do not know and have no way of knowing.

For instance, I can open my 4th editionSteel Manual (1967) to page 2-122 and look at diagram #9 and see this very problem, along with the formulas for stresses and deflections. (if you don't have the same edition, the page and diagram number are likely different, but the diagram will be the same).

We also know that these diagrams are idealized renditions of common problems (hence the triangle pin and roller at the ends) and that assist in finding reasonable solutions.

Message 39: He has perfectly shown how people with little or no knowledge of the subject at hand still feel they can wade in and point out what they see to be deficiencies in the diagram and therefore dismiss the question as nonsense.
When in fact to someone who knows the subject matter, the diagram is clear, consise and as has been shown in this thread, makes the point that Taz wanted to make quite well.

Indeed. This is why learning the technical "language" of a field is critical if you are going to discuss it intelligently.

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


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Replies to this message:
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Taz
Member (Idle past 1124 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 72 of 137 (665935)
06-20-2012 1:10 AM
Reply to: Message 71 by RAZD
06-19-2012 9:05 PM


Re: the technical "language" used ...
RAZD writes:

Indeed. This is why learning the technical "language" of a field is critical if you are going to discuss it intelligently.


This is why sometimes I wonder if I'm driving honest to god scientists nuts by weighing in my opinion or have a layman explanation of something as I understand it.

Edit.

A question comes to mind. Is it possible to have an intelligent debate without the technical language of the field? Sounds like a PNT to me...

Edited by Taz, : No reason given.


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Heathen
Member
Posts: 1039
From: Brizzle
Joined: 09-20-2005


Message 73 of 137 (665939)
06-20-2012 2:29 AM
Reply to: Message 46 by jar
06-18-2012 12:15 PM


And no, I do not deal with such things when I walk across a bridge.

You deal with the bridge when you cross it, a diagram as the one above REPRESENTS a bridge (or similar)

I'm not about to get into a semantics pissing contest with you regarding the meaning of "nonsense". You're on your own there.


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 Message 46 by jar, posted 06-18-2012 12:15 PM jar has responded

Replies to this message:
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Heathen
Member
Posts: 1039
From: Brizzle
Joined: 09-20-2005


Message 74 of 137 (665940)
06-20-2012 2:32 AM
Reply to: Message 71 by RAZD
06-19-2012 9:05 PM


Re: the technical "language" used ...
exactly.
And in a few cases in this thread responders have not attempted to learn the technical language and/or study the subject, but give their best guess based upon their "common Sense" or simply decide the problem is meaningless.

Taz's point proved.


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Heathen
Member
Posts: 1039
From: Brizzle
Joined: 09-20-2005


Message 75 of 137 (665941)
06-20-2012 2:38 AM


here's a little Bending moment/Shearforce diagram calculator. should give some hints
http://www.glerok.com/sbd/
  
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