The electrical systems of all houses built prior to 1960

Question

The electrical systems of all houses built prior to 1960 contain copper wiring, which is superior to aluminum wiring. The plumbing systems of some houses built in this time period, however, contain lead pipes, which can contaminate a house's water supply. But there is good news. At least some houses containing copper wiring are not built on landfills, and no houses built on landfills have plumbing containing lead pipes. 
 
If the statements above are true, then which of the following must also, on the basis of those statements, be true?

(A) Some houses built on landfills do not contain copper wiring in their electrical systems 
 (B) Some houses built on landfills do contain copper wiring in their electrical systems 
 (C) Some houses with lead pipes in their plumbing systems also contain copper wiring in their electrical systems 
 (D) Some houses built prior to 1960 do not contain copper wiring in their electrical systems 
 (E) S  ome houses with lead pipes in their plumbing systems are not houses other than those built on landfills

MuskaanMittal · Answer

Question Explanation

The question stem asks which of the following must also...be true, so this is an inference question. Do not bother breaking the passage into its conclusion, premise, and assumption for inference questions. Instead, focus on what the passage states directly. The correct answer must be true based on the facts in the passage. The passage presents wiring and pipe information for houses built prior to 1960. The passage states that all houses built prior to 1960 contain copper wiring, and that some houses built in this time period...contain lead pipes. The passage then states that at least some houses containing copper wiring are not built on landfills, and that no houses built on landfills...have lead pipes. Evaluate the answer choices.

Choice A: No. This choice is out of scope. While the passage does state some houses containing copper wiring are not built on landfills, there is no information about whether other types of houses are built on landfills.

Choice B: No. This choice is out of scope. The passage states that at least some houses containing copper wiring are not built on landfills, but it provides no information about whether some houses with copper wiring are built on landfills.

Choice C: Correct. The passage states that all houses built prior to 1960 contain copper wiring, and some houses built in this time period...contain lead pipes. Therefore, it must be true that Some houses with lead pipes...also contain copper wiring.

Choice D: No. Some houses built prior to 1960 do not contain copper wiring is a reversal. The passage states that all houses built prior to 1960 contain copper wiring.

Choice E: No. Some houses with lead pipes...are not houses other than those built on landfills is a reversal. The passage states that no houses built on landfills have...lead pipes.

The correct answer is choice C.

Mehakgyl · Answer

KarishmaB   bb   Bunuel  
Would one of you be able to share the solution for this question?

bb · Answer

This is an interesting question.

1. I feel it’s a little bit sloppy. The question tells us which of the following must also be true. The word also implies in addition to the facts stated above but choice C is pretty much the restatement of the facts from above, so it’s hard to pick it as the choice that also must be true because it is basically what the passage told us.

2. I feel B could be a good contender. It would not pass on the LSAT because it’s claiming the opposite and just simply because we know that at least some houses with copper wiring were not built on the landfill, doesn’t always allow us to automatically assume that somehow houses must have been built because perhaps maybe old houses were not built on the landfill but we only know that we’re guaranteed at least some and maybe others were not checked. So per the higher standard LSAT, B is out, which leaves us with C. but again it doesn’t meet the also condition in my mind but it is truly at least.

Anyone feels different about the question?

I hope it helps  Mehakgyl

Mehakgyl · Answer

I selected B because the passage states that all houses built prior to 1960 contain copper wiring. Additionally because of the last line of the passage we know that atleast some houses are built on landfills. 
Hence if all houses contain copper wiring and atleast some houses are built on landfills, then those houses built on landfills must contain copper wiring. 
Where am I going wrong here?

bb · Answer

We only know that some houses containing copper wiring are not built on landfills but we don’t know that any are built on landfills... these are not mutually exclusive.

The electrical systems of all houses built prior to 1960

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The electrical systems of all houses built prior to 1960

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

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My Rewards