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