broall wrote:
If the public library shared by the adjacent towns of Redville and Glenwood were relocated from the library’s current, overcrowded building in central Redville to a larger, available building in central Glenwood, the library would then be within walking distance of a larger number of library users. That is because there are many more people living in central Glenwood than in central Redville, and people generally will walk to the library only if it is located close to their homes.
Which one of the following, if true, most strengthens the argument?
(A) The public library was located between Glenwood and Redville before being moved to its current location in central Redville.
(B) The area covered by central Glenwood is approximately the same size as that covered by central Redville.
(C) The building that is available in Glenwood is smaller than an alternative building that is available in Redville.
(D) Many of the people who use the public library do not live in either Glenwood or Redville.
(E) The distance that people currently walk to get to the library is farther than what is generally considered walking distance.
Source: LSAT
Same passage with different stem question:
LINK MGMAT explanation -->
The author uses two premises...
More people live in central Glenwood than in central Redville
+
Generally, people will walk to a library only if it's close to their home
To validate a conclusion...
A library in central Glenwood would be within walking distance for more people than would a library in central Redville
For all Strengthen questions, we know going in that the evidence presented is not going to be sufficient to prove the conclusion reached. We want to make sure to consider this gap between evidence and conclusion carefully before moving on to the answer choices.
Why doesn't the evidence presented here validate the conclusion?
The author is assuming that because more people live in central Glenwood, more people will be within walking distance of a library in central Glenwood. Is this valid?
Let's imagine that Central Glenwood is Los Angeles, population 3 million, and Central Redville is Irvine, population 200,000. Does that mean any library in Los Angeles is going to have more people within walking distance than any library in Irvine? Not necessarily. The library in Los Angeles might happen to be in a commercial area that doesn't have a lot of homes, and the library in Irvine might be in the middle of it's most crowded neighborhood.
In order to use information about population to prove something about population density (people within a certain radius of a certain building), we need to have information about how big a space this population lives in. Answer choice (B), by giving us this information, helps us prove that Glenwood is more densely populated than Redville.