#24- Downtown Petropolis boasted over 100 large buildings

[akalsi]

I'm having difficulty understanding why answer E is an assumption that is required in this argument.
Originally I had chosen option B. I thought this was right because it would explain that the number of large buildings is significantly lower now than before. But why would this answer be incorrect and answer E be the correct answer?

-Anoop

[Nikki Siclunov]

Hi Anoop,

The author is worried about the economic decline of Petropolis, because 60 of the 100 large buildings in Petropolis have been demolished over the past 5 years, and the total number of such buildings is supposedly an indicator of economic health.

From your remarks, I can see that you made the same (unwarranted) assumption as the author: you don't really know whether the number of large buildings in Petropolis has actually declined! All you know is that 60 of the 100 large buildings from 5 years ago have been demolished. What if 200 new large buildings went up over the same period of time? The author only provides information about how many buildings have been demolished, without telling us if any new buildings have been built.

This is precisely why answer choice (E) is the correct answer to this Assumption question: the author assumes that the number of demolished buildings is higher than the number of new buildings, so that we have a net loss of large buildings in Petropolis. Try the Assumption Negation Technique and ask yourself this: if 60+ large buildings went up in downtown Petropolis during the past five years, would this weaken the conclusion? Of course: this would show that Petropolis is not necessarily in economic decline.

Answer choice (B) is not an assumption upon which the argument depends, and its logical opposite has no effect on the conclusion. Even if Petropolis had significantly more than 100 buildings at some point in the past, it can still be in a serious state of economic decline today.

Hope this helps!

[LSATer]

What is the best way to negate answer choice E?

I negated it as "Not significantly fewer than 60 new large buildings have been built in downtown Petropolis during the past 5 years".

Since not significantly fewer than 60 can still include 58 or 59, I used that reasoning to select E.

So I guess my question is, does "not significantly fewer than 60" technically include numbers below and above 60?

I hope this question makes sense.

LSATer

[Luke Haqq]

Hi LSATer,

Yes, you negated the statement correctly, and "not significantly fewer than 60" in this context would include numbers below (like 58 and 59) and above 60.

Answer (E) is an assumption that is required by the argument. The 60 buildings being demolished is taken to be evidence why "it is clear that downtown Petropolis is in a serious state of economic decline." This might be clear evidence, but only of it were the case that the loss of 60 buildings hadn't been recouped since the time 5 years ago that they were demolished. This is what (E) gets across.

Hope that helps!

[LSATer]

Thank you!