PT 32 Section 1 Question 24

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PT 32 Section 1 Question 24

Post by deputamadre » Wed Feb 24, 2010 10:54 pm

This question has lots and lots of information in it. Going throught the answer choices, I find myself going back to the stimulus and re-reading parts to see if the answer choice is "strongly suported by the science journalist's statements".

1) How do I approach a question like this?

2) What is the negation of answer choice C? Do I turn both no's to yes' or only one of the no's to yes'?

Is the answer (c) because a brown dwarf that does not have a functional nuclear funace must have lithium in that atmosphere, which leads to (c), basically saying that any celestial object that does not have lithium is a brown dwarf?

Thanks beforehand

Atlas LSAT Brian

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Re: PT 32 Section 1 Question 24

Post by Atlas LSAT Brian » Thu Feb 25, 2010 2:41 am

This is a tough question. Lots of detail here.

Here's my best shot at answering your question.

1) You should note the facts in the argument and choose an answer that MUST be true, and provable.

2) I don't think it matters. Negating choices is pretty much only helpful on assumption questions and some flaw questions. Contra-positives are helpful on questions like these, though. Flip and negate.
Choice (C) essentially says that a CO with no Li is NOT a BD. The contra-positive of that would be something like "a BD is a CO with Li"

I'm not sure that's even helpful on this particular problem b/c it's kind of confusing. Here's my take on the problem:

Note the facts in the argument -- this is the hard part, constructing all the conditional statements, and their contra-positives when possible

1. BD = CO w/more mass than planets, and less mass than stars

2. stars as massive as Sun --> Li (b/c mixing incomplete)
star with no Li --> not a star as massive as the Sun

3. stars less massive than Sun --> no Li (b/c fully mixed and consumed)
star with Li --> not a star less massive than the Sun

4. BD --> Li (b/c no fully functional furnace, Li cannot be consumed)
no Li --> not a BD

(A) CO with Li --> star less massive than Sun?
we know only about stars with Li, nothing about other COs that might have Li. And even if (A) said "stars with Li" instead of CO, statement 3 above contradicts this.

(B) Co with Li --> furnace that incompletely mixed
nope. The only thing we know for sure that leads to an "incomplete mix..." is a "star as massive as the Sun." See statement 2 above.

(C) CO w/o Li --> not BD
absolutely. See statement 4 above. Note that translating this choice into conditional language is tricky.

(D) CO with Li --> as much mass as Sun (or more)
no support for this above

(E) CO less massive than BD --> no Li
again, no support.

This is a super tough problem. Hard to explain in type. Hope that helps!


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Re: PT 32 Section 1 Question 24

Post by Shrimps » Thu Feb 25, 2010 2:42 am

(A) is out of scope. The journalist never said anything about non-stars.
(B) is identical to (A). "Any.. object", unless a term like this is explicitly mentioned in the text, is a pretty obvious indicator the answer choice is wrong.
(D) and (E) again generalize, but in the negative direction. The text never talked about objects other than stars and brown dwarves.

Even if you cannot identify the correct question right away, remember, all the other four answers are WRONG - in this case, wrong for a very obvious reason: they start talking about celestial objects other than stars and brown dwarves, of which nothing is mentioned in the text.

First sentence: "brown dwarves identified by.. whether or not lithium is present in their atmosphere". All good, but the journalist then does not say explicitly whether brown dwarves have or don't have lithium in their atmosphere (it's a very poorly written text, but then, LSAT test makers love them). Instead, he rambles about stars for a bit and then finishes: "A brown dwarf".. has "lithium that cannot be consumed". Ah, so brown dwarves DO have lithium in their atmosphere!

(C) says if it doesn't have lithium in its atmosphere, then it's not a brown dwarf. Which is what we're looking for.

Really, convoluted-language questions are fairly obvious once you dissect them. This question is no harder than a reading comprehension question once you dissect and understand this horrid, meandering style in which the stimulus and the answers are written. I don't know what to recommend to improve your ability to read convoluted texts. Practice, practice, and more practice, I suppose.

"No object that has no lithium in its atmosphere is a brown dwarf" - "ANY object that has no lithium in its atmosphere is NOT a brown dwarf". It's not formal logic, per se, but it would look like this: Objects with no lithium in atmosphere <--|--> brown dwarf, I suppose. A Venn-type diagram could also help.

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