Critical Reasoning

31. All actors are exuberant people and all exuberant people are extroverts, but nevertheless it is true that some shy people are actors.

If the statements above are true, each of the following must also be true EXCEPT:
A. Some shy people are extroverts.
B. Some shy extroverts are not actors.
C. Some exuberant people who are actors are shy.
D. All people who are not extroverts are not actors.
E. Some extroverts are shy.


to me all seems valid:-(
how to solve this one.

imo - d

it is question of ** reasoning which says

a-b-c-d

not d - not c - not b - not a

hemant_rajput wrote:31. All actors are exuberant people and all exuberant people are extroverts, but nevertheless it is true that some shy people are actors.

If the statements above are true, each of the following must also be true EXCEPT:
A. Some shy people are extroverts.
B. Some shy extroverts are not actors.
C. Some exuberant people who are actors are shy.
D. All people who are not extroverts are not actors.
E. Some extroverts are shy.


to me all seems valid:-(
how to solve this one.

A.Incorrect. "Some shy people are extroverts." The passage claims that there are shy actors. Because all actors are extroverts then a shy actor is also an extrovert.

B.Correct. "Some shy extroverts are not actors." One of the main points stated by the passage is that ALL actors are extroverts. Therefore, the claim that a shy extrovert is not an actor contradicts the explicit statement that ALL actors are extroverts. Lets also note that "shy" is not the same thing as "introverted," which means that part of the confusion of this question stems from failing to understand that a person can be a "shy extrovert" but cannot be an "introverted extrovert" because the latter is contradictory. This way, you can read "Some shy extroverts are not actors" as "Some extroverts are not actors", a statement that clearly contradicts the passage given the scope of the information with which we are working.

C.Incorrect. "Some exuberant people who are actors are shy." The passage makes clear that there can be "shy extroverts", and because "All actors are exuberant people and all exuberant people are extroverts," it follows that some exuberant people who are actors will be "shy extroverts"

D.Incorrect. "All people who are not extroverts are not actors." The statement is supported by the passage because the passage makes clear that all actors are extroverts.

E.Incorrect. "Some extroverts are shy." The passage makes clear that extroverts can be shy because being shy is not the same thing as being introverted. Thus, in order to effectively answer this question, we have to be attune to this type of intricate word play that substitutes a similar meaning word for words that have more specific meanings, such as the use of "shy" in place of "introverted."

I hope that is clear,

Albert


www.gmatquestions.org (200+ free practice questions with step-by-step video tutorials, launching 7/29/13)

This is an LSAT question. It is from the October 1994 exam, Logical Reasoning section 1, Question 25.

This is an example of formal logic that is possibly a bit beyond what is on the GMAT. I am going to explain this in formal logic as I would for the LSAT. You can diagram the stimulus this way:

If Actor ---> exuberant ----> extrovert.
Shy people some Actors.

Do you see what I have done? The arrow indicates the "therefore" or "then" statement. So we know that if someone is an actor he is exuberant and must also be an extrovert. So you can say that all actors are extroverts.

The other statement just indicates that some shy people are actors. Now, we can even put these statements together to say:

Shy people some Actors ---> exuberant ----> extrovert.

This means that some shy people are Actors and are therefore exuberant and extroverts. So we can actually say that some shy people are extroverts!

Use the diagram above on the answer choices to see which "must be true". Eliminate those that must be true on this "except" question.

A) Some shy people are extroverts. -- We just concluded this!
B) Some shy extroverts are not actors. -- Wait on this one it is not clearly true since we do not know about those who are "not actors" rather than analyze it too move on and come back if necessary. If the other four are eliminated this will be the correct answer.
C) Some exuberant people who are actors are shy. -- This is true because all actors are exuberant so if any shy people are actors they are exuberant people. And we know that there are shy people who are actors, so this must be true.
D) All people who are not extroverts are not actors. This is true. It is called the "contrapositive" Since we know that all actors are extroverts it must be true that those are fail to be extroverts cannot be actors.
E) Some extroverts are shy. This is true because you can always reverse a "some" statement. So If I say that "some judges are women" it is pretty clear that "some women are judges" as well. In this case is A is true then E is automatically true as well.

B is the OA. Does that help?

David,

Answer choice B actually seems quite clear, when not based on the standards of formal logic. The GMAT critical reasoning section is not a test based on formal logic but on logical reasoning, which is not the same thing. The strategy must be adaptive and not formal. So even if we do not know anything about people who are not actors, we cannot overlook the fact that the statement (B) does not support the passage. Therefore, I would think that the "non-certainty" should be a clue as to the fact that B is the correct answer and not as an occasion to proclaim uncertainty: uncertainty is a resource here, not something that does not fit formal logic and therefore cannot be "certain". It may be useful to use the lack of certainty as a clue to B being correct considering what the question is explicitly asking for, namely, a statement with faulty reasoning.

Albert

Albert -

My name is not Veritas, although I do always tell the truth.

This is an LSAT question. As I stated above. "It is from the October 1994 exam, Logical Reasoning section 1, Question 25."

As I stated

This is an example of formal logic that is possibly a bit beyond what is on the GMAT

In other words this is a question that you would not see on the GMAT.

Anyway you have your own perspective and I appreciate that. Keep up the good work.