LSAT 146 | Section 3 | Logical Reasoning: Q5

LR Question 5 Explanation

QUESTION TEXT: Resident: Data indicates that 30 percent of the houses…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: At least 60% of our houses have a big problem.

REASONING: 30% of houses have drainage problems, and 30% of houses are unsafe due to defects.

ANALYSIS: The author makes the mistake of thinking the two groups can’t overlap: it’s possible that the houses with drainage issues all have structural defects. In that case, only 30% of houses would have their integrity threatened.

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1. The number of houses is irrelevant. This question is talking about the percentage of houses with a problem. You can still have a percentage even with a small number of houses.
2. This is a very tempting answer. If you prephrased the question and didn’t read all the answers, you might have fallen for this trap.
    
   This answer sounds like it’s saying the two groups can overlaps, but that’s not what it says. The issue wasn’t whether houses are unsafe. It’s whether they have a structural issue that makes them unsafe. (i.e. A house could be unsafe because a bear lives inside, but that’s not a structural issue)
3. It doesn’t matter what’s easier to fix. The argument is only about how common the issue is.
4. This doesn’t contradict the argument. It’s possible that 60% of houses have threatened integrity, and 40% of houses don’t. The author’s conclusion would be correct, but this answer would also be true, because 40% is “many”.
5. CORRECT. If this is true, then fewer than 60% of houses could have their integrity threatened.