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  LiveWire / Teen Forums / Religion & Philosophy / Viewing Topic

Simple Logic Homework
Replies: 10Last Post Sep. 19, 2008 6:19pm by Doghouse
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I'm doing some homework for my Intro to Logic course, and a very basic/easy question has popped up that I can't seem to answer; the online program that I have to do it on continues to insist that my answers are incorrect (out of 23 questions this is the only one I can't get). Either I'm making an incredibly stupid and short sighted mistake, or there is some sort of error with the program. I ask you logicians out there to translate this sentence into its symbolic form:

Susan will start working at home if, but not only if, Peter's mother helps with the rent

Dictionary:
M = Peter's mother will help with the rent
S = Susan will start working at home


9:04 am on Sep. 19, 2008 | Joined: Oct. 2005 | Days Active: 923
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Permious

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M -> S?  

If Peter's mother helps with the rent Susan will start working at home.  

I dunno

i mean there's if and only if for a reason, so I assume if means the same as if but not only if. :/

Post edited at 9:11 am on Sep. 19, 2008 by Permious

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9:11 am on Sep. 19, 2008 | Joined: July 2008 | Days Active: 81
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Khadgar

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I'm no logician, but can't that just be an if/then, since M guarantees S?

M → S


9:12 am on Sep. 19, 2008 | Joined: Feb. 2006 | Days Active: 681
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Permious

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Quote: from Permious at 9:11 am on Sep. 19, 2008

M -> S?  

If Peter's mother helps with the rent Susan will start working at home.

I dunno

i mean there's if and only if for a reason, so I assume if means the same as if but not only if. :/


from wiki

"A ⇒ B means if A is true then B is also true; if A is false then nothing is said about B."

so yeah, if that cunt doesn't help with the rent, it says nothing about whether or not Susan will work at home

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9:13 am on Sep. 19, 2008 | Joined: July 2008 | Days Active: 81
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Khadgar

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Quote: from Permious at 9:13 am on Sep. 19, 2008

"A ⇒ B means if A is true then B is also true; if A is false then nothing is said about B."

so yeah, if that cunt doesn't help with the rent, it says nothing about whether or not Susan will work at home


Actually, that one looks more correct.


9:14 am on Sep. 19, 2008 | Joined: Feb. 2006 | Days Active: 681
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DayXTripper

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Quote: from Khadgar at 9:12 am on Sep. 19, 2008

I'm no logician, but can't that just be an if/then, since M guarantees S?

M → S


m doesn't guarantee s though.

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9:16 am on Sep. 19, 2008 | Joined: July 2005 | Days Active: 392
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Quote: from DayXTripper at 9:16 am on Sep. 19, 2008

Quote: from Khadgar at 9:12 am on Sep. 19, 2008

I'm no logician, but can't that just be an if/then, since M guarantees S?

M → S


 

m doesn't guarantee s though.


Susan will Start working at home if Peter's mom pays the rent

why doesn't M guarantee S? :S

i hate this shit so much :/

Post edited at 9:19 am on Sep. 19, 2008 by Permious

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9:18 am on Sep. 19, 2008 | Joined: July 2008 | Days Active: 81
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Quote: from DayXTripper at 9:16 am on Sep. 19, 2008

Quote: from Khadgar at 9:12 am on Sep. 19, 2008

I'm no logician, but can't that just be an if/then, since M guarantees S?  

 M → S


m doesn't guarantee s though.


Sure it did.

Susan will start working at home if, but not only if, Peter's mother helps with the rent.

The "but not only if" part just says that this is not the only condition which would cause the outcome.

So, saying M → S (if M, then S) is correct, but saying that M ≡ S (if and only if M, then S) is not.


9:19 am on Sep. 19, 2008 | Joined: Feb. 2006 | Days Active: 681
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edit... I see it now. Doh!

The Oath, I'm reading the page you sent me...

Post edited at 9:23 am on Sep. 19, 2008 by DayXTripper

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9:20 am on Sep. 19, 2008 | Joined: July 2005 | Days Active: 392
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M → S was one the first things I wrote down, so now I'm pretty sure it was an error on the program's side, not mine. Thanks to all that attempted to help.

5:24 pm on Sep. 19, 2008 | Joined: Oct. 2005 | Days Active: 923
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Doghouse

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ow. that statement isn't coherent... basically she'll do it either way.... i think its a trick question for sure.

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