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- Fri Jan 21, 2011 12:00 am
#22740
Complete Question Explanation
Must Be True-SN. The correct answer choice is (C)
The stimulus in this argument contains two conditional statements:
Note that since this a Must Be True question, we must accept both of the above premises as true. Thus, we cannot claim that the second premise is a Mistaken Reversal of the first premise. This would only occur if we were attempting to infer the second premise just on the basis of the first premise. In this case Elena has stated both premises as facts and we thus accept them as true. This generates an interesting situation for Elena where every dog that growls at her is a white poodle, and every white poodle growls at her. Thus, each condition is both sufficient and necessary for the other condition. We can diagram such a statement as:
The double-arrow indicates that both conditions must occur together, or that alternately neither of the two conditions will occur. There are no other possibilities in such a situation. With that in mind, let's look at the answer choices.
Answer choice (A): This answer is incorrect because Elena may have seen other white dogs—her comments are limited to dogs she saw that growled at her. So, for example, she may have seen a white Husky, and all we would know was that it didn't growl at her.
Answer choice (B): This answer is wrong because Elena only discusses the white poodles she saw; there may have been gray ones, and she may well have seen them, they just didn't growl at her. But she didn't mention it, so this answer fails the Fact Test.
Answer choice (C): This is the correct answer choice. We know that the only dogs that growled at Elena were white poodles, so no other dog growled at her. That would include gray dogs of any type (or black dogs, tan dogs, etc) .
The gray dogs aspect here causes many people to eliminate this answer immediately on the basis that gray dogs weren't discussed in the stimulus. But, is that really accurate? As Alex rightly notes below:
In other words, be careful with the "umbrella" that certain words and phrases create. This is especially when an absolute or powerful word is being used, such as "only" in this case. those words draw a line around what is included, and then the umbrella of the idea extends outward to include those not included as well. So, if I say "The only book genre l like is science fiction," then that means we can start talking about other genres (romance, fantasy, etc) and we'll know I don't like them. Knowing how this works can help unlock a number of tough LSAT Logical Reasoning questions, especially those in the Must Be True category.
Answer choice (D): This answer is is incorrect since it states that "All the white dogs that Elena saw growled at her," whereas her statements in the stimulus were specific to white poodles. Thus, we don't that this answer is not true, but we also don't know that it is undeniably true, and since that's the standard of the question stem, this answer is wrong. In other words, this answer could be true since maybe she only saw white poodles, but we're asked for what must be true, so this doesn't meet that standard since there could have been other white non-poodles that she saw.
Note that the problem with (D) is the phrase "white dogs;" we know that the white poodles growled at Elena, but we don't know about all the white dogs she saw.
Answer choice (E): This answer is similar to (B), and is wrong because Elena only discusses the white poodles she saw; there may have been gray ones, and she may well have seen them, they just didn't growl at her. But she didn't mention it, so this answer fails the Fact Test.
Must Be True-SN. The correct answer choice is (C)
The stimulus in this argument contains two conditional statements:
- DG = dog growled WP = white poodle
Premise 1: DG WP
Premise 2: WP DG
Note that since this a Must Be True question, we must accept both of the above premises as true. Thus, we cannot claim that the second premise is a Mistaken Reversal of the first premise. This would only occur if we were attempting to infer the second premise just on the basis of the first premise. In this case Elena has stated both premises as facts and we thus accept them as true. This generates an interesting situation for Elena where every dog that growls at her is a white poodle, and every white poodle growls at her. Thus, each condition is both sufficient and necessary for the other condition. We can diagram such a statement as:
- DG WP
The double-arrow indicates that both conditions must occur together, or that alternately neither of the two conditions will occur. There are no other possibilities in such a situation. With that in mind, let's look at the answer choices.
Answer choice (A): This answer is incorrect because Elena may have seen other white dogs—her comments are limited to dogs she saw that growled at her. So, for example, she may have seen a white Husky, and all we would know was that it didn't growl at her.
Answer choice (B): This answer is wrong because Elena only discusses the white poodles she saw; there may have been gray ones, and she may well have seen them, they just didn't growl at her. But she didn't mention it, so this answer fails the Fact Test.
Answer choice (C): This is the correct answer choice. We know that the only dogs that growled at Elena were white poodles, so no other dog growled at her. That would include gray dogs of any type (or black dogs, tan dogs, etc) .
The gray dogs aspect here causes many people to eliminate this answer immediately on the basis that gray dogs weren't discussed in the stimulus. But, is that really accurate? As Alex rightly notes below:
- "This is a common misconception - that if there is something unrecognizable in the answer choices, it must be new and has to be wrong. But as we can see here, that's not necessarily true (I'd venture to guess, in fact, that the LSAT testmakers were counting on people to see the word gray here and rule it out automatically), because this isn't actually "new" information.
The key is to think logically about the answer choices, and if they are proved by the stimulus. Elena states that "While I was at the dog show, every dog that growled at me was a white poodle" - so we can conclude that no other types of dogs growled at her. that means no black dogs, no yellow dogs, no gray dogs, etc. This proves answer choice (C): "At the dog show, no gray dogs growled at Elena." We can think of a gray dog as a non-white dog, which we know could not have growled at Elena, and thus we have a direct inference from what was said, and not an answer that contains new information. Hope this helps!"
In other words, be careful with the "umbrella" that certain words and phrases create. This is especially when an absolute or powerful word is being used, such as "only" in this case. those words draw a line around what is included, and then the umbrella of the idea extends outward to include those not included as well. So, if I say "The only book genre l like is science fiction," then that means we can start talking about other genres (romance, fantasy, etc) and we'll know I don't like them. Knowing how this works can help unlock a number of tough LSAT Logical Reasoning questions, especially those in the Must Be True category.
Answer choice (D): This answer is is incorrect since it states that "All the white dogs that Elena saw growled at her," whereas her statements in the stimulus were specific to white poodles. Thus, we don't that this answer is not true, but we also don't know that it is undeniably true, and since that's the standard of the question stem, this answer is wrong. In other words, this answer could be true since maybe she only saw white poodles, but we're asked for what must be true, so this doesn't meet that standard since there could have been other white non-poodles that she saw.
Note that the problem with (D) is the phrase "white dogs;" we know that the white poodles growled at Elena, but we don't know about all the white dogs she saw.
Answer choice (E): This answer is similar to (B), and is wrong because Elena only discusses the white poodles she saw; there may have been gray ones, and she may well have seen them, they just didn't growl at her. But she didn't mention it, so this answer fails the Fact Test.
Dave Killoran
PowerScore Test Preparation
Follow me on X/Twitter at http://twitter.com/DaveKilloran
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PowerScore Test Preparation
Follow me on X/Twitter at http://twitter.com/DaveKilloran
My LSAT Articles: http://blog.powerscore.com/lsat/author/dave-killoran
PowerScore Podcast: http://www.powerscore.com/lsat/podcast/