LSAT 106 – Section 1 – Question 12

LSAT 106 - Section 1 - Question 12

June 1999

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT106 S1 Q12
+LR
Necessary assumption +NA
Conditional Reasoning +CondR
A
10%
166
B
76%
168
C
9%
165
D
4%
157
E
1%
164
132
149
165
 +Medium 152.148 +SubsectionHarder

J.Y.’s explanation

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People who say that Dooney County is flat are clearly wrong. On flat land, soil erosion by water is not a problem. Consequently, farmers whose land is flat do not build terraces to prevent erosion. Yet I hear that the farms in Dooney County are dotted with terraces.

Summary
Dooney County isn’t flat. How do we know? The author sets up a conditional argument with two key premises:
(1) If farmland is flat, then farmers don’t build terraces to prevent erosion on that land.
(2) In Dooney County, there are terraces on farmland (at least, so the author hears).

Notable Assumptions
The author tries to use premise (2) to trigger the contrapositive of premise (1). But he relies on several assumptions to make that contrapositive work:

- What he’s heard about terraces on Dooney County’s farms is true. (Otherwise, there’s no reason to think there are any terraces.)

- Some terraces in Dooney County were built to prevent erosion. (If they were for another purpose, they tell us nothing about whether the land is flat.)

- Some terraces in Dooney County were built by farmers. (If other people built them all, we can’t infer anything about the land.)

A
the only cause of soil erosion is water
It’s the presence of terraces, not the specifics of erosion, that the argument depends on. Even if other causes of erosion exist, we know that on flat land, water-caused erosion isn’t a problem, and so any time farmland is flat, farmers won’t build terraces to prevent erosion.
B
there are terraces on farmland in Dooney County which were built to prevent soil erosion
This must be true for the author to infer that Dooney County is not flat. If (B) weren’t true—if there are no terraces that were specifically built to prevent soil erosion—then whatever terraces are there tell us nothing about whether the land is flat.
C
terraces of the kind found on farmland in Dooney County have been shown to prevent soil erosion
Whether the terraces happen to prevent erosion is irrelevant. What matters is what the terraces were built to do. For the argument to work, the terraces must have been specifically built (by farmers) to prevent erosion. Otherwise, the presence of terraces means nothing.
D
on flat land there is no soil erosion
It’s the presence of terraces, not the specifics of erosion, that the argument depends on. Even if erosion occurs on flat land, we know that water-caused erosion isn’t a problem, and so any time farmland is flat, farmers won’t build terraces to prevent erosion.
E
the only terraces in Dooney County are on farmland
Too strong. The argument only requires that at least some terraces in Dooney County are on farmland (because it’s the presence of farmland terraces that can help tell us whether the land is flat). Whether or not terraces also exist on other kinds of land is irrelevant.

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LSAT PrepTest 106 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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