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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
Statement A is false. We can't infer from the text that " Bridges built before about 1907 were built without thorough mathematical analysis and, therefore, were unsafe for the public to use". Statement E can be infered
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
D. Only a more rigorous application of mathematical analysis to the design of the Quebec Bridge could have prevented its collapse.
RIGHT, it clearly says only the new rule or new analysis could have prevented the collapse


E. Prior to 1907 the mathematical analysis incorporated in engineering rules of thumb was insufficient to completely assure the safety of bridges under construction.
WRONG, because it says only new analysis will help that are under construction and that to it says Prior to 1907 the existing mathematical analysis as thumb rule is unsafe for buildings which are under construction. If so many buildings would have collapsed prior to 1907.

Please help me out to clear my thinking.
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
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ravikrishna1979 wrote:
D. Only a more rigorous application of mathematical analysis to the design of the Quebec Bridge could have prevented its collapse.
RIGHT, it clearly says only the new rule or new analysis could have prevented the collapse


E. Prior to 1907 the mathematical analysis incorporated in engineering rules of thumb was insufficient to completely assure the safety of bridges under construction.
WRONG, because it says only new analysis will help that are under construction and that to it says Prior to 1907 the existing mathematical analysis as thumb rule is unsafe for buildings which are under construction. If so many buildings would have collapsed prior to 1907.

Please help me out to clear my thinking.


The passage says that twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis - but it has not been mentioned whether such analysis could prevent collapse. It is as well possible that even after the analysis, some bridges collapse. hence statement D cannot be inferred.

I am not sure what is you point about option E - you yourself concluded that "thumb rule is unsafe" - so you are actually supporting that option E is correct.
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
why not B - if cooper was present, he could have stopped the construction... any one can enlighten me on the same... thanks in advance
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
vishwash wrote:
why not B - if cooper was present, he could have stopped the construction... any one can enlighten me on the same... thanks in advance


If B is correct can you explain these lines of the passage.

As a direct result of the inquiry that followed, the engineering "rules of thumb" by which thousands of bridges had been built around the world went down with the Quebec Bridge.

The incident was more of a result of the use of "rule of thumb" rather absence of this guy. moreover what if he is present and could not have done those calculation.

IMO E
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
OFFICIAL ANSWER:

The question requires the examinee to identify the response that can be properly inferred from the passage. The passage indicates that the Quebec Bridge disaster in 1907 and the inquiry that followed caused the engineering “rules of thumb” used in construction of thousands of bridges to be abandoned. Since the Quebec Bridge disaster in 1907 prompted this abandonment, it can be inferred that these were the rules of thumb under which the Quebec Bridge was being built when it collapsed and that these were the rules of thumb used in bridge building before 1907. Further, since the Quebec Bridge collapsed while under construction and the rules of thumb being used were abandoned as a result, it can be inferred that the rules of thumb used in building the Quebec Bridge and bridges prior to 1907 were insufficient to completely assure the safety of bridges under construction. Finally, since the alternative to the old engineering rules of thumb that was adopted was to “depend on far more rigorous applications of mathematical analysis,” it can be inferred that it was the mathematical analysis incorporated in the engineering rules of thumb used prior to 1907 that made them insufficient to completely assure the safety of bridges under construction. Thus, (E) is the credited response.

Response (A) is incorrect. (A) asserts that the lack of thorough mathematical analysis in the construction of bridges before about 1907 was sufficient to establish that those bridges were unsafe for the public to use. But, the rules of thumb used in bridge construction before 1907 were abandoned because they were not sufficient to establish that the bridges being constructed using them were safe when under construction. It does not follow that the lack of more rigorous or thorough mathematical analysis in the rules of thumb was sufficient to establish that the bridges built before about 1907 using them were unsafe even while under construction, let alone for the public. In fact, some, or even all, may have been quite safe. In addition, the passage gives evidence only about the safety of bridges built before 1907 while they were under construction. It is silent on whether bridges built before about 1907 were safe when open for use by the public.

Response (B) is incorrect in claiming that Cooper’s absence from the construction site caused the breaking off of the cantilever. The passage does not establish that, had Cooper been at the site, he could have successfully intervened to prevent the cantilever from breaking off. By freezing the project, he might have spared lives by stopping work, but there is nothing in the passage to indicate that he necessarily would have prevented the collapse.

Response (C) is incorrect; there is no evidence in the passage about why nineteenth-century engineers relied on their rules of thumb.

Response (D) is also incorrect. While the passage suggests that a more rigorous application of mathematical analysis would have prevented the collapse of the bridge, it offers no evidence that it is the only way the collapse could have been prevented. For example, it might have been prevented had corrective measures been taken in time.

OPTION: E
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Re: During construction of the Quebec Bridge in 1907, the bridge’s designe [#permalink]
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EchelonStrike2016 wrote:
During construction of the Quebec Bridge in 1907, the bridge’s designer, Theodore Cooper, received word that the suspended span being built out from the bridge’s cantilever was deflecting downward by a fraction of an inch. Before he could telegraph to freeze the project, the whole cantilever arm broke off and plunged, along with seven dozens workers, into the St. Lawrence River. It was the worst bridge construction disaster in history. As a direct result of the inquiry that followed, the engineering “rules of thumb” by which thousands of bridges had been built went down with the Quebec Bridge. Twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis.

Which one of the following statements can be properly inferred from the passage?


(A) Bridges built before about 1907 were built without thorough mathematical analysis and, therefore, were unsafe for the public to use.

(B) Cooper’s absence from the Quebec Bridge construction site resulted in the breaking off of the cantilever.

(C) Nineteenth-century bridge engineers relied on their rules of thumb because analytical methods were inadequate to solve their design problems.

(D) Only a more rigorous application of mathematical analysis to the design of the Quebec Bridge could have prevented its collapse.

(E) Prior to 1907 the mathematical analysis incorporated in engineering rules of thumb was insufficient to completely assure the safety of bridges under construction.


The question requires us to find a logical inference from the given statements, i.e., the passage.

The passage provides the following information:
-The context is the construction of the Quebec Bridge in 1907; the bridge’s designer, Theodore Cooper, received word that the suspended span being built out from the bridge’s cantilever was deflecting downward by a fraction of an inch.
- Before he could telegraph to freeze the project, the whole cantilever arm broke off and plunged, along with seven dozens workers, into the St. Lawrence River.
- It was the worst bridge construction disaster in history. As a direct result of the inquiry that followed, the engineering “rules of thumb” by which thousands of bridges had been built went down with the Quebec Bridge.
-Twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis.

As can be seen from the above-mentioned information, the process of measurement on which bridge construction were based played an important role and after the disaster, were changed as it was felt that the previous process was inadequate.

This option mentions bridges that are already built and have been in use for a considerable amount of time. This option does not deal with the process of construction during which the measurements play an important role. So, Option A can be eliminated.

All the sentences in the passage mention measurements, so the indication is that a lack of proper measurements probably had something to do with the disaster. There is no information to indicate that Cooper’s absence created the problem or that his presence could have averted the disaster. So, Option B can be eliminated.

The passage only states that there were engineering “rules of thumb” by which thousands of bridges had been built; there is no mention or indication of any other method of measurement. In fact, the passage states that twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis. So, Option C can be eliminated.

This option has the adverb ‘only’, which is to be treated with caution. The passage describes an incident and mentions a result of that incident. There is no information to indicate what might have prevented the incident. The passage does state that twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis, but that is not enough information to suggest that nothing else would have prevented the disaster. So, Option D can be eliminated.

Option E states that the mathematical analysis incorporated in engineering rules of thumb prior to 1907 was insufficient to completely assure the safety of bridges under construction. This option sums up the idea that the disaster was probably caused by a gap in the process of measurement. Therefore E is the most appropriate option.

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Re: During construction of the Quebec Bridge in 1907, the bridges designe [#permalink]
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Re: During construction of the Quebec Bridge in 1907, the bridges designe [#permalink]
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