Q10 - If the public library

[jas770]

Could someone explain why "B" is the correct answer to question 10? It doesn't make sense how area would effect the overall population.

[ManhattanPrepLSAT2]

Notice the core relationship in this argument:

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.

[Sweetangel]

For the secondary weaken question, how does B weaken the conclusion, "the library would then be within walking distance of a larger number of library users"? The argument isn't about how many people WILL actually access the library, but about how many COULD. I don't see how the library's increased potential accessibility is weakened by stating that less people would use the library if relocated (irrelevant?).

[tommywallach]

Hey SweetAngel,

That's question 11, which has a separate thread.

-t

[Mab6q]

Great explanation by Mike above. Let me just add why the other answer choices are incorrect.

A. this is absolutely irrelevant.

C. is also irrelevant. The author says if it was moved.....

D. another irrelevant answer because we aren't concerned with that group of people.

E. Might be tempting because of how it's worded. However, all it tells us is that the people who are currently walking to the library are walking more than what is considered walking distance. However this is irrelevant because we are not necessary interested in the number of people walking but the number of users who are within walking distance.