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Economic collapse

by varun7nurav » Thu Sep 29, 2011 2:06 am
45. To avoid economic collapse, Russia must increase its GNP by 20%. However, due to the structure of its economy, if the 20% threshold is reached, then a 40% increase in GNP is achievable.
Assuming that the above statements are true, which one of the following must also be true?
(A) If ethnic strife continues in Russia, then a 20% increase in GNP will be unattainable.
(B) If a 40% increase in Russia's GNP is impossible, its economy will collapse.
(C) If Russia's GNP increases by 40%, its economy will not collapse.
(D) If the 20% threshold is reached, then a 40% increase in GNP is achievable and a 60% increase is probable.
(E) If Russia's economy collapses, then it will not have increased its GNP by 40%.
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by gunjan1208 » Thu Sep 29, 2011 2:37 am
Is this E. (Causation problem) let me know the OA. I should be able to explain that further.
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by chetansharma » Thu Sep 29, 2011 3:41 am
varun7nurav wrote:45. To avoid economic collapse, Russia must increase its GNP by 20%. However, due to the structure of its economy, if the 20% threshold is reached, then a 40% increase in GNP is achievable.
Assuming that the above statements are true, which one of the following must also be true?
(A) If ethnic strife continues in Russia, then a 20% increase in GNP will be unattainable.
(B) If a 40% increase in Russia's GNP is impossible, its economy will collapse.
(C) If Russia's GNP increases by 40%, its economy will not collapse.
(D) If the 20% threshold is reached, then a 40% increase in GNP is achievable and a 60% increase is probable.
(E) If Russia's economy collapses, then it will not have increased its GNP by 40%.
IMO the answer is C. What is the OA?

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by varun7nurav » Thu Sep 29, 2011 12:13 pm
Even I think it should be C
but the OA is B.
And moreover, the explanation also sounds plausible.

Solution:
Answer: (B)
Explanation: Diagramming will show this seemingly difficult problem to be simply an application of the contrapositive rule of logic: in an if-then statement, negating the conclusion also negates the premise. The sentence "To avoid economic collapse, Russia must increase its GNP by 20%" can be reworded as "if Russia does not increase its GNP by 20%, its economy will collapse." This in turn can be symbolized as
not20%->Collapse
Where the arrow, ->, stands for "if ..., then ....

Next, symbolize the clause "if the 20% threshold is reached, then a 40% increase is achievable" as
20%->40%
Applying the contrapositive to this statement yields
not40%->not20%

Using the transitive property (If a = b and b = c, then a = c) to combine this with the first symbol statement yields
not40%->Collapse
In other words, if a 40% increase in GNP is unattainable, the economy will collapse. This is precisely what choice (B) states. The answer is (B).



P.S: Source is a from a file shared by 'pupgust', member of BTG.
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by chetansharma » Fri Sep 30, 2011 12:26 am
varun7nurav wrote:Even I think it should be C
but the OA is B.
And moreover, the explanation also sounds plausible.

Solution:
Answer: (B)
Explanation: Diagramming will show this seemingly difficult problem to be simply an application of the contrapositive rule of logic: in an if-then statement, negating the conclusion also negates the premise. The sentence "To avoid economic collapse, Russia must increase its GNP by 20%" can be reworded as "if Russia does not increase its GNP by 20%, its economy will collapse." This in turn can be symbolized as
not20%->Collapse
Where the arrow, ->, stands for "if ..., then ....

Next, symbolize the clause "if the 20% threshold is reached, then a 40% increase is achievable" as
20%->40%
Applying the contrapositive to this statement yields
not40%->not20%

Using the transitive property (If a = b and b = c, then a = c) to combine this with the first symbol statement yields
not40%->Collapse
In other words, if a 40% increase in GNP is unattainable, the economy will collapse. This is precisely what choice (B) states. The answer is (B).



P.S: Source is a from a file shared by 'pupgust', member of BTG.
Well... from the explanation answer can be B

I cannot give such a detailed explanation (as in mathematics :D) but here is what I thought.
Clearly A and D are not even the contenders for the answer. From remaining B,C and D

B states that if the GNP does not increase by 40%, the economy will collapse. True (But isn't it stated in the premise. To avoid the economy collapse, the GNP has to increase by 20%. And if 20% is achieved 40% is achievable)
So are the statements C & E. But in a different way. Aren't they?
But of B,C and E ,C seemed more accurate.
May if someone can explain why C and E are wrong, it would be helpful. :)

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by David@VeritasPrep » Fri Sep 30, 2011 6:34 am
Got a PM on this one...

This is pretty much a re-write of an LSAT question. For some reason I cannot find the original question but it did not talk about Russia and the percentages were different like 10% and 20% instead of 20% and 40%. Anyway this is the simple transitive property. Like a math problem.

If A is required and A brings B with it automatically then if you do not see B then A is not there either. So let's say something like this. If you can get a 720 on the GMAT then you can certainly get a 730. So if you cannot get a 730 then a 720 is impossible for you. Now let's add the requirement that without a 720 you will not be accepted. Well if the 720 is possible only when the 730 is possible, then we can say that if you are not capable of a 730 (and therefore not capable of a 720) you will not be accepted.

Chetan asks is choice B not basically stated in the premises...this is an inference question, so the correct answer must be true - so if the answer choice restates a premise then good! That means it certainly must be true!! Never eliminate the answer to an inference question because it appears to restate a premise. In this case it does not. You have to connect the dots and that is not restating but in general NEVER eliminate for this supposed problem. Remember you are looking for Must Be True.

As to choices C and E we can eliminate these as not being "Must Be True." This is a matter of what are called "Necessary" and "Sufficient" conditions. It is necessary that the economy grow by 20% (and therefore be able to grow by 40%) in order to avoid collapse, but it does not mean that this is the only requirement. There is a scenario where the GNP grows by 40% but let's say inflation is 100% and the economy still collapses. Choice C could be false. We are not told in the stimulus that the only requirement to avoid collapsing is the 20% growth, just that this growth is a requirement.

Choice E is the reverse of choice C and is wrong for exactly the same reasons. In fact C and E are really the same answer! As I mentioned above there are other reasons that the economy could collapse. My inflation example will serve here. So if the economy collapses it may still have grown 40% (but inflation is 100%) So E is not must be true either.

Since this is a take off of an LSAT question it uses a bit more formal logical than is typical of the GMAT.

Hope that helps...
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by apex231 » Fri Sep 30, 2011 6:22 pm
Hi David,

Option B states that if 40% growth is not possible then economy will collapse.

However it's not stated that achieving 20% threshold is the only factor involved in increasing GNP by 40%. There may be other factors involved too. So, even if the economy grows by less than 40% , let's say 30%, the economy will not collapse.

So how can we so conclusively say that if 40% increase in Russia's GNP is impossible then its economy will collapse?

Thanks!
David@VeritasPrep wrote:Got a PM on this one...

This is pretty much a re-write of an LSAT question. For some reason I cannot find the original question but it did not talk about Russia and the percentages were different like 10% and 20% instead of 20% and 40%. Anyway this is the simple transitive property. Like a math problem.

As to choices C and E we can eliminate these as not being "Must Be True." This is a matter of what are called "Necessary" and "Sufficient" conditions. It is necessary that the economy grow by 20% (and therefore be able to grow by 40%) in order to avoid collapse, but it does not mean that this is the only requirement. There is a scenario where the GNP grows by 40% but let's say inflation is 100% and the economy still collapses. Choice C could be false. We are not told in the stimulus that the only requirement to avoid collapsing is the 20% growth, just that this growth is a requirement.

Choice E is the reverse of choice C and is wrong for exactly the same reasons. In fact C and E are really the same answer! As I mentioned above there are other reasons that the economy could collapse. My inflation example will serve here. So if the economy collapses it may still have grown 40% (but inflation is 100%) So E is not must be true either.

Since this is a take off of an LSAT question it uses a bit more formal logical than is typical of the GMAT.

Hope that helps...
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by David@VeritasPrep » Sat Oct 01, 2011 8:59 am
Apex -

You said,
However it's not stated that achieving 20% threshold is the only factor involved in increasing GNP by 40%. There may be other factors involved too. So, even if the economy grows by less than 40% , let's say 30%, the economy will not collapse.


Actually if you look at the stimulus - achieving 20% GUARANTEES being able to achieve 40%. Please note that you are correct when you talk about other factors required to actually reach 40%. Yet actually reaching 40% is not required in the stimulus or in the correct answer.

The stimulus says "if the 20% threshold is reached, then a 40% increase in GNP is achievable." This does not say that 40% will be achieved, just that it is "achievable."

Similarly answer choice B says "(B) If a 40% increase in Russia's GNP is impossible, its economy will collapse." Notice that it DOES NOT say that if Russia fails to achieve the 40% the economy will collapse, only that if it is "impossible" to achieve it will collapse.

I know this is subtle and more so than anything you would see on GMAT test day. Perhaps going back to my above analogy will help. Above I said what if a 720 is required for admission to your MBA program of choice. And what if I said that anyone who actually earns a 720 is a person who is capable of a 730. Notice I did not say that person would actually earn the 730. Maybe she gets distracted or unlucky, but the capability must be there. So we could say that if a 730 is impossible for her then she will not earn the 720 and won't get into her MBA program of choice.
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