Downtown Petropolis boasted over 100 large buildings 5 years ago.

Question

Downtown Petropolis boasted over 100 large buildings 5 years ago. Since then, 60 of those buildings have been demolished. Since the number of large buildings in a downtown is an indicator of the economic health of that downtown, it is clear that downtown Petropolis is in a serious state of economic decline.

Which one of the following is an assumption required by the argument?

(A) The demolitions that have taken place during the past 5 years have been evenly spread over that period.
(B) There have never been significantly more than 100 large buildings in downtown Petropolis.
(C) Most of the buildings demolished during the past 5 years were torn down because they were structurally unsound.
(D) The large buildings demolished over the past 5 years have been replaced with small buildings built on the same sites.
(E) Significantly fewer than 60 new large buildings have been built in downtown Petropolis during the past 5 years.

ajaygaur319 · Answer

Pre-thinking -  We need to somehow prove that no new buildings were created after demolishing these 60 buildings.

(A) The demolitions that have taken place during the past 5 years have been evenly spread over that period. -  Irrelevant 
(B) There have never been significantly more than 100 large buildings in downtown Petropolis. -  Irrelevant 
(C) Most of the buildings demolished during the past 5 years were torn down because they were structurally unsound. -  If such was the case then the reason is not economic. It weakens the argument 
(D) The large buildings demolished over the past 5 years have been replaced with small buildings built on the same sites. -  It shows that the some small buildings are formed upon demolishing large buildings. Negating this won't result in complete breakdown of conclusion 
(E) Significantly fewer than 60 new large buildings have been built in downtown Petropolis during the past 5 years. -  Negating this will completely break down the conclusion that there are at least some significant number (around 60) buildings are constructed.

David nguyen · Answer

Downtown Petropolis boasted over 100 large buildings 5 years ago. Since then, 60 of those buildings have been demolished. Since the number of large buildings in a downtown is an indicator of the economic health of that downtown, it is clear that downtown Petropolis is in a serious state of economic decline.

100 buildings were built
60 buildings were demolished
Less Buildings -> Economic Decline

What is the leap of the conclusion here?

The author says that 60 buildings were demolished, leading to a total reduction in number of buildings. Is this necessarily true? The only thing that we know is that buildings were being taken down, but we don't know whether there were any that were being built at the same time period. What If more buildings were being built than being demolished? Perhaps those older buildings were being replaced with a better one. Then the economy actually would be in a better state. Without considering this, the conclusion remains unsubstantiated and open to debate.

Let's check out the options.

Which one of the following is an assumption required by the argument?

This doesn't solve the statistical issue. The demolitions were taken within 1, 2, 3, or 5 years evenly or oddly does not matter. (A) is out.
 
"Not Significantly" means it is possible that there had been 110 large buildings in downtown after demolitions and new construction. This, if anything, weakens the argument.
 
Because they were structurally unsound, they were going to be replaced with the stronger one. This fails to solve the problem with the statistic again. (C) is out.
 
This matches our thinking, solving the number of buildings problem. Now we have the same number of buildings replacing the old ones. So this must be the correct answer right? No not necessarily. Even though replacing with smaller buildings might indicate that the economy is in decline. Let's negate this: The LB demolished over the past 5 years have NOT been replaced with small buildings built on the same sites. Hmm, This leaves the possibility that less than 60 buildings could have been built to replace the old ones. The argument still holds true under this. (D) is out.
 
This matches our thinking. It eliminates the possibilities that more than 60 buildings could be built; hence, the economy is certain in decline.

Only (E) is left. (E) is correct.

Subhrajyoti · Answer

As i understand, in assumption question we are not allowed to take outside info, so in that case why is E the correct answer

David nguyen · Answer

Hi  Subhrajyoti , I am happy to help you with this question: "In Assumption question, one must not take outside information as the correct answer choice". Your thought is absolutely correct, but i think the way the answer choice was phrase confused you.

I assume that you understand what the difference between  Supporter Assumption  and  Defender Assumption . If you don't, let me explain.

Supporter Assumption:  It's purpose is to link or bridge the gap between the premise and the conclusion. Hence, anything that is presented in the conclusion but not in the premises must be mentioned in the answer choice.

Defender Assumption : This assumption is different to SA because its purpose is to ELIMINATE the possible situations/causes that MUST NOT happen. It will break the conclusion apart unless the possible situations/cases do not occur. 
+ Note that : Possible Situations/Cases = New Information. However, what we are doing is to eliminate that new information instead of adding it to the argument

Now, let's see what the answer chocie E say:

They have built significantly fewer than 60 new large buildings in downtown Petropolis during the past 5 years. In other words, They have not built significantly more than or equal to 60 new large buildings.

As you can see when the answer is rephrased, the original version shows us that it is possible that in the past 5 years, there were fewer than 60 new large buildings were built. The author used this assumption to eliminate the possibility that "they have not built > = 60 buildings''. Hence, this is not considered new information.

If the answer were phrased in this way: "60 or more new large buildings have been built", then it would have been considered new information. — This might be the correct answer for Weakening question type.

Does that make any sense to you?

GMAT0010 · Answer

According to EGMAT, an assumption does 2 functions:
1. Bridges the gap between premise and conclusion
2. Negates anything that weakens the argument.
Here, if 60 buildings are demolished and if that leads to economic downfall, then...
Ok, what if the number of buildings constructed > number of buildings destroyed? The argument falls right ?

None of the answer choices seem to work out..
Hope this helps!

None of the answer choices seem to work out.. Hope this helps!

anirudh1993 · Answer

Downtown Petropolis boasted over 100 large buildings 5 years ago. Since then, 60 of those buildings have been demolished. Since the number of large buildings in a downtown is an indicator of the economic health of that downtown, it is clear that downtown Petropolis is in a serious state of economic decline.

Which one of the following is an assumption required by the argument?

(A) The demolitions that have taken place during the past 5 years have been evenly spread over that period.
(B) There have never been significantly more than 100 large buildings in downtown Petropolis.
(C) Most of the buildings demolished during the past 5 years were torn down because they were structurally unsound.
(D) The large buildings demolished over the past 5 years have been replaced with small buildings built on the same sites.
 (E) Significantly fewer than 60 new large buildings have been built in downtown Petropolis during the past 5 years.

E is the correct answer.
Lesser Large Buildings ->Economic decline
So we have to assume that the demolished buildings were replaced with a handful of buildings, which is indicative of an Economic decline.

unraveled · Answer

Downtown Petropolis boasted over 100 large buildings 5 years ago. Since then, 60 of those buildings have been demolished. Since the number of large buildings in a downtown is an indicator of the economic health of that downtown, it is clear that downtown Petropolis is in a serious state of economic decline.

Which one of the following is an assumption required by the argument?

(A) The demolitions that have taken place during the past 5 years have been  evenly spread  over that period.
(B) There have never been  significantly more than 100 large buildings  in downtown Petropolis.
(C) Most of the buildings demolished during the past 5 years were torn down because they were  structurally unsound .
(D) The large buildings demolished over the past 5 years have been replaced with small buildings built on the same sites.
(E) Significantly fewer than 60 new large buildings have been built in downtown Petropolis during the past 5 years.

Only D and E are contenders. 
D loses out since it leaves a scope wherein it's still possible that almost same number of large building were built but on other locations.

Choosing E over D is little difficult then going POE-way.

Answer E.

brianmontanaweb · Answer

The question wants us to focus on assumptions in the argument. First thing we notice is there were "over 100 large buildings 5 years ago" and "60 of those buildings have been demolished", we'll hold on to these phrases since they seem important right now. The conclusion states that large buildings are an economic health indicator. We already have a vague idea of the assumption that more buildings haven't been built than have been demolished.

A and C are out of scope.

D would strengthen the argument but doesn't state the assumption. Eliminate.

B is interesting but the argument relies on the demolition of buildings for the assumption. So incorrect.

E is correct since the argument relies on "more buildings haven't been built than have been demolished", which can be restated as "less buildings have been built than demolished".

VerbalBot · Answer

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Downtown Petropolis boasted over 100 large buildings 5 years ago.

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Downtown Petropolis boasted over 100 large buildings 5 years ago.

Prep Toolkit

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

More than Quant/Verbal Abilities: Speed vs. Accuracy

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From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards