Q22 - Paulsville and Longtown cannot both be ...

[soyeonjeon]

can we please go over this one? I am failing to spot the logical structure of the stimulus. I do see the answer but when I draw the map of the stimulus, it seems to be a one wiht a flawed reasoning.
Thanks in advance.

[mrsam723]

Can't stop in P + L (P->~L, L->~P)
~S->P->~L
And we know ~S
So ~L

[justindebouvier7]

This problem can be diagrammed nicely and that will help us solve the problem effectively.

So what do we know?

P-->~L
L-->~P
~P-->S
~S
--------------
~L (Key inference:P)

Although this is a parallel argument, one key inference is that since the candidate is not going to ~S then he/she must be going to P via the contrapositive of the ~P-->S. Therefore, she must got to P and cannot go to L.

Now, we need to find an answer choice within the stimulus that matches something to what we have above and that is exactly choice B. Although it is quite time-consuming, especially since it is a parallel flaw question, I like to diagram the answer choices.

Regarding B:
P-->~C
C-->~P
~M-->P
~M
---------------
~C (Key inference:P)

Notice that everything that we have in answer choice B is exactly the same as diagrammed above. The only thing different in this diagram is that we didn't use the contrapostive while in the stimulus it did.

[ohthatpatrick]

Great responses.

Just in case anyone is concerned about the other answers ...

In each case we need
i. a mutually exclusive pair (P and L, in the original)
ii. a conditional statement that involves one of those two things and some third thing (~S-->P, in the original)
iii. a statement of fact about the third thing that triggers the conditional statement and tells us that one half of the mutually exclusive pair must happen (~S, in the original ... which allows us to infer P)
iv. a conclusion that says the other half of the mutually exclusive pair is therefore ruled out (~L, in the original)

(A) is super close
R and G are the mutually exclusive pair.
R --> S is the conditional statement with some third thing.
~S is the statement of fact that triggers the conditional statement; here it allows us to infer ~R.
The problem is we wanted to know that R is happening, so that we can conclude that G cannot happen. Instead, this tells us that R is NOT happening.

(C)
S and S are the mutually exclusive pair (already, I doubt this one)
C --> ~S is the conditional
S is the statement of fact that triggers the conditional, allowing us to infer ~C.
The conclusion is about C, rather than about the mutually exclusive pair.

(D)
P and INE are the mutually exclusive pair.
PRC --> ~P and ~INE (this one dies right here)

(E)
S and R are the mutually exclusive pair.
But we never get a third thing, so this one dies at the second sentence.

Hope this helps.

[mwalton444]

For future reference, if the question stem does not mention that the argument you must parallel is flawed, can you assume the logic is not flawed? Because I read this very quickly and thought it was flawed. It would help save time if I could be 100% sure it was not flawed.

[tommywallach]

Yep!