Those who have the ability to fully concentrate are always of above-average intelligence. Also, being successfully tr...

Naz October 20, 2013

The sentence "being successfully trained in speed-reading will usually be accompanied by an increased ability to concentrate," cannot be diagrammed because it is not a sufficient/necessary statement. The "usually" is what should clue you to this. That means that sometimes this occurs, but sometimes it may not occur.

We diagram the first sentence:

AFC ==> AAI
not AAI ==> not AFC

(A) is CORRECT because if people are able to fully concentrate, according to the passage, they WILL be of above average intelligence. Therefore, it CANNOT be true that "some people can speed-read, and are able to fully concentrate, but are of below-average intelligence." Since this is a could be true EXCEPT question, answer choice (A) is our answer because it cannot be true.

(B) is incorrect because it can be true. Other than the fact that those who are successfully trained in speed-reading will USUALLY be accompanied by an increased ability to concentrate, we are not given any information of their intelligence. The passage tells us something about those who are "successfully trained in speed-reading" and not about those who "can speed-read." Therefore, it CAN be true that "all people who can speed-read are of above-average intelligence."

(C) is incorrect because it can be true. The sufficient condition in the passage is having the "ability to fully concentrate." If one has the ability to fully concentrate then it must be true that they are of above average intelligence. Remember that the necessary condition of the principle rule and the necessary condition of the contrapositive can exist together. Therefore, in this situation, it is possible to have someone who is of above average intelligence (the necessary condition of the principle rule) and who does not have the ability to fully concentrate (the necessary condition of the contrapositive).

(D) is incorrect because it can be true. We have no information in the passage that contradicts answer choice (D). Therefore, there's no reason why it can't be true.

(E) is incorrect because it can be true. Just as with answer choice (D), we have no information in the passage that contradicts this answer choice. Therefore, there is no reason as to why it cannot be true.

Hope that helps! Let me know if you have any other questions!

Batman October 22, 2013

Many thanks, always

Alex January 25, 2017

When explaining C, you said that it is possible to have a necessary condition of the principle rule and a necessary condition of the contrapositive. How is that possible? It wasn't mentioned in the lecture at all about Sufficient and Necessary Condition where I think it first mentioned these concepts. Please explain. Thank you.

Mehran January 29, 2017

@Alex so this question is asking us what "could be true EXCEPT."

So four of these answer choices are possible, whereas one of these answer choices is not possible, i.e. cannot be true.

As stated above, the first sentence is diagrammed as follows:

AFC ==> AAI
not AAI ==> not AFC

(C) states, "Many people of above-average intelligence are unable to fully concentrate."

"Above-average intelligence" is our necessary condition, so it tells us nothing else.

It is possible these people are able to fully concentrate, but it is also possible they are not.

Let's use the example from our Sufficient & Necessary lesson to clarify this point:

"All carrots are vegetables."

C ==> V
not V ==> not C

The equivalent of (C) in this example would be, "Many vegetables are not carrots."

This is definitely possible as there are vegetables other than carrots.

What cannot be true, however, is a carrot that is not a vegetable, or in this case, someone who is able to fully concentrate but who is not above average intelligence, i.e. (A), "able to fully concentrate, but are below-average intelligence."

Hope that helps! Please let us know if you have any other questions.

Reina December 6, 2019

@mehran is this true all of the time (that the necessary conditions can exist together) and is this used often on the LSAT? I didn't catch that when I first did the question on my own so I want to make sure I understand it and how commonly it is used.