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All bridges built from 1950 to 1960 are in serious need of

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All bridges built from 1950 to 1960 are in serious need of [#permalink] New post 21 Sep 2010, 14:24
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54% (03:03) correct 45% (02:05) wrong based on 214 sessions
All bridges built from 1950 to 1960 are in serious need of rehabilitation. Some bridges constructed in this period, however, were built according to faulty engineering design. That is the bad news. The good news is that at least some bridges in serious need of rehabilitation are not suspension bridges, since no suspension bridges are among the bridges that were built according to faulty engineering design.
If the statements above are true, then, on the basis of those statements, which one of the following must be true?

(A) Some suspension bridges are not in serious need of rehabilitation.
(B) Some suspension bridges are in serious need of rehabilitation.
(C) Some bridges that were built according to faulty engineering design are in serious need of rehabilitation.
(D) Some bridges built from 1950 to 1960 are not in serious need of rehabilitation.
(E) Some bridges that were built according to faulty engineering design are not bridges other than suspension bridges.

What's wrong with B?
[Reveal] Spoiler: OA

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Re: suspension bridges [#permalink] New post 21 Sep 2010, 15:37
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The question asks for what MUST be true based on the information given. For formal logic questions like this one, it is very helpful, and maybe even necessary, to diagram the relationships between and among the different elements. The diagram for this stimulus is as follows:

Faulty <--some--> built 1950-60 --all--> in serious need of rehab --some are not --> suspension bridges <--none--> faulty

Now let's see which of the answer choices MUST BE TRUE according to our diagram.

A) Some suspension bridges are not in serious need of rehabilitation.

- Nope, not necessarily. We know that some bridges in serious need of rehab are not suspension bridges, but this does not necessarily mean that some suspension bridges are not in serious need of rehab. To simplify further, suppose there are 10 bridges in serious need of rehab. 3 of them are not suspension bridges (satisfies the requirement that some are not suspension bridges). What about the other 7? Could 1 or more or even all of them be suspension bridges? Absolutely. Now what if there are only 7 suspension bridges, and they all happen to be the 7 that need rehab? Then we can say that all suspension bridges are in serious need of rehab. Hence, A does not necessarily have to be true.

(B) Some suspension bridges are in serious need of rehabilitation.

- Again, this does not necessarily have to be true. In fact, there is nothing in the stimulus that supports this. This could be true, it could be false.

(C) Some bridges that were built according to faulty engineering design are in serious need of rehabilitation.

- This is the correct answer. Looking at our diagram, we see that some bridges that were built according to faulty design where built between 1950-1960, and all bridges built between 1950 and 1960 are in serious need of rehab. Hence, it follows that some bridges built according to faulty design are in serious need of rehab.

One can argue that the stimulus only states that some bridges built between 1950-1960 are in serious need of rehab, and not the other way around. But consider the following scenario: 10 bridges were built during 1950-1960. 3 of them were built according to faulty design (satisfying the requirement in the stimulus). From this, we can clearly see that at least 3 bridges built according to faulty design were built during 1950-1960. Hence, some bridges built according to faulty design were built during 1950-60.

(D) Some bridges built from 1950 to 1960 are not in serious need of rehabilitation.

- This directly contradicts the information in the stimulus and is therefore false.

(E) Some bridges that were built according to faulty engineering design are not bridges other than suspension bridges.

- Nothing in the stimulus supports this. Could be true, could be false. We are looking for the answer that must be true.
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Re: All bridges built from 1950 to 1960 are in serious need of [#permalink] New post 02 Feb 2013, 22:38
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I think the key to this problem lies in the "at least some bridges in serious need of rehabilitation are not suspensions bridges". Could be some, could be all. If all [are not suspension bridges], only C stands as true.
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Re: suspension bridges [#permalink] New post 21 Sep 2010, 14:28
B is not wrong as it is true that some bridges will need rehabilitation. It is just not as true as C which goes into greater detail saying that some bridges that were built according to faulty engineering design are in serious need of rehabilitation.

So C is just more precise than B.
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Re: suspension bridges [#permalink] New post 21 Sep 2010, 14:39
We have to assume that the choices refer to bridges between 1950 to 1960

Wrong, since all bridges from 1950 to 1960 need rehab (A) Some suspension bridges are not in serious need of rehabilitation.

Very clearly given in the statement. Agreed it is TRUE, but then it has already been stated in the statement that "... some bridges in serious need of rehabilitation are not suspension bridges ..." (B) Some suspension bridges are in serious need of rehabilitation.

(C) Some bridges that were built according to faulty engineering design are in serious need of rehabilitation.

Wrong, since specified that all bridges from 1950 to 1960 need rehab (D) Some bridges built from 1950 to 1960 are not in serious need of rehabilitation.

Wrong, not bridges other than suspension bridges means - suspension bridges (E) Some bridges that were built according to faulty engineering design are not bridges other than suspension bridges.

Going back to the remaining choices, C can be inferred and B is given fact (does not require inference).
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Re: suspension bridges [#permalink] New post 21 Sep 2010, 16:35
thanks Xmarksthespot, the diagramming illustrates the conclusion well....
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Re: suspension bridges [#permalink] New post 21 Sep 2010, 18:01
noboru wrote:
All bridges built from 1950 to 1960 are in serious need of rehabilitation. Some bridges constructed in this period, however, were built according to faulty engineering design. That is the bad news. The good news is that at least some bridges in serious need of rehabilitation are not suspension bridges, since no suspension bridges are among the bridges that were built according to faulty engineering design.
If the statements above are true, then, on the basis of those statements, which one of the following must be true?

(A) Some suspension bridges are not in serious need of rehabilitation.
(B) Some suspension bridges are in serious need of rehabilitation.
(C) Some bridges that were built according to faulty engineering design are in serious need of rehabilitation.
(D) Some bridges built from 1950 to 1960 are not in serious need of rehabilitation.
(E) Some bridges that were built according to faulty engineering design are not bridges other than suspension bridges.

What's wrong with B?


Another thing wrong with (B) is that the question is asking which one MUST be true. The article only claims that "at least some bridges... are not suspension bridges." That means it's possible that NONE of the bridges are suspension bridges, in which case (B) would be false.
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Re: suspension bridges [#permalink] New post 21 Sep 2010, 18:11
Good answer, Xmarksthespot, Kudos.
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Re: suspension bridges [#permalink] New post 23 Sep 2010, 20:00
I also pick C ....but was literally lost in so many bridges ....noboru +1 for posting good questions ....cheers .....
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Re: suspension bridges [#permalink] New post 23 Sep 2010, 21:12
My choice is also C and the reasoning is same as all the above...
Appreciate u Xmarks...thanks for ur explanation..
+1 for you..
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Re: suspension bridges [#permalink] New post 24 Sep 2010, 18:49
I almost fell for B as well.
+1 for Xmarksthespot
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Re: suspension bridges [#permalink] New post 03 Oct 2010, 20:49
C for me. I think doing a Venn diagram would have been faster.
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Re: suspension bridges [#permalink] New post 04 Oct 2010, 07:55
arundas wrote:
C for me. I think doing a Venn diagram would have been faster.


Can someone explain in terms of Venn Diagram please?
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Re: suspension bridges [#permalink] New post 05 Oct 2010, 10:04
Got it wrong .Took B as answer.
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Re: suspension bridges [#permalink] New post 04 Apr 2011, 20:55
The answer is C.
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Re: suspension bridges [#permalink] New post 07 Apr 2011, 04:32
Guys Nowhere in the stimulus is it mentioned that suspension bridges were among the bridges that were built between 1950 - 60 . B and A can be straightaway eliminated .
Anybody agreeing on what i stated .
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Re: suspension bridges [#permalink] New post 03 May 2011, 09:29
'The good news is that at least some bridges in serious need of rehabilitation are not suspension bridges'

that does not mean some bridges built from 1950 to 1960 are suspension bridges. hence B does is incorrect . C is the answer
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Re: suspension bridges [#permalink] New post 17 May 2011, 00:05
between B and C, B is not explicitly stated in the argument neither can it be inferred using fact test.

C can be inferred using fact test.
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Re: suspension bridges [#permalink] New post 17 May 2011, 01:00
noboru wrote:
All bridges built from 1950 to 1960 are in serious need of rehabilitation. Some bridges constructed in this period, however, were built according to faulty engineering design. That is the bad news. The good news is that at least some bridges in serious need of rehabilitation are not suspension bridges, since no suspension bridges are among the bridges that were built according to faulty engineering design.
If the statements above are true, then, on the basis of those statements, which one of the following must be true?

(A) Some suspension bridges are not in serious need of rehabilitation.
It may be true if there were no suspension bridge built during the period. We don't know that.
(B) Some suspension bridges are in serious need of rehabilitation.
At least some suspension bridge not in serious need of rehab ranges from at least some to at most all.
(C) Some bridges that were built according to faulty engineering design are in serious need of rehabilitation.
True. Some bridges is a subset of all bridges. If all bridges are in need, some bridges will definitely be in need irrespective of the reason.
(D) Some bridges built from 1950 to 1960 are not in serious need of rehabilitation.
Directly contradicts the first line of the passage.
(E) Some bridges that were built according to faulty engineering design are not bridges other than suspension bridges.
Directly contradicts: "no suspension bridges are among the bridges that were built according to faulty engineering design"

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Re: All bridges built from 1950 to 1960 are in serious need of [#permalink] New post 30 Jan 2013, 03:27
Really confusing this one;

I went with C over B because for C i could not find any possible reason for it not to be true, even though the answer choice doesn't focus on bridges from 1950 to 1960 specifically.
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Re: All bridges built from 1950 to 1960 are in serious need of   [#permalink] 30 Jan 2013, 03:27
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