LSAT 124 – Section 2 – Question 20

LSAT 124 - Section 2 - Question 20

December 2007

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Question QuickView	Type	Tags	Answer Choices	Curve	Question Difficulty	Psg/Game/S Difficulty	Explanation
PT124 S2 Q20	+LR +Exp	Flaw or descriptive weakening +Flaw Conditional Reasoning +CondR Quantifier +Quant	A 28% 159 B 53% 166 C 0% 143 D 1% 156 E 17% 158	152 161 170	+Hardest	145.571 +SubsectionMedium

J.Y.’s explanation

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On some hot days the smog in Hillview reaches unsafe levels, and on some hot days the wind blows into Hillview from the east. Therefore, on some days when the wind blows into Hillview from the east, the smog in Hillview reaches unsafe levels.

Summarize Argument

The author concludes that there are some days when both of the following occur: (1) the wind blows into Hillview from the east, and (2) the smog in Hillview reaches unsafe levels. This is based on the fact that there are some hot days on which the smog in Hillview reaches unsafe levels, and that there are some hot days on which the wind blows into Hillview from the east.

Identify and Describe Flaw

The author assumes that some of the hot days on which the smog reaches unsafe levels are the same hot days on which the wind blows in from the east. This overlooks the possibility that the hot days on which the smog reaches unsafe levels are simply different days from the hot days on which the wind blows in the from east.

If “Some A are B” and “Some A are C,” we cannot conclude “Some B are C.” This is because B and C might not overlap within the set of A.

mistakes a condition that sometimes accompanies unsafe levels of smog for a condition that necessarily accompanies unsafe levels of smog

The author does not assume that anything “necessarily accompanies” unsafe levels of smog. The author believes that some days with unsafe smog levels are days on days with the east wind, but that doesn’t imply unsafe smog is always accompanied by east wind.

fails to recognize that one set might have some members in common with each of two others even though those two other sets have no members in common with each other

The author fails to recognize that although the set of “hot days” has some days in common with the “unsafe smog days” and some in common with “east wind days,” the “unsafe smog days” and “east wind days” don’t have to have any days in common.

uses the key term “unsafe” in one sense in a premise and in another sense in the conclusion

The word “unsafe” does not take on different meanings in this argument. It means “not safe.”

contains a premise that is implausible unless the conclusion is presumed to be true

(D) describes circular reasoning, which isn’t what happens here. Accepting the premises does not require that we already accept there are some days with both unsafe smog and east wind.

infers a particular causal relation from a correlation that could be explained in a variety of other ways

The argument does not assert any causal relationships. The claim that there are some days that have both the east wind and unsafe smog does not assert that the east wind causes smog to be blown in or that the smog causes the east wind.

LSAT 124 – Section 2 – Question 20

LSAT 124 - Section 2 - Question 20

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J.Y.’s explanation

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Review Results

LSAT PrepTest 124 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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