To avoid economic collapse, Russia must increase its GNP by 20%. Howev

I don't understand why C is wrong.
SajjadAhmad please post OE.

40% increase is a necessary condition but not a sufficient condition. It is the same like - to get a good score in GMAT, I need to study hard. So, studying hard is a necessary condition, not a sufficient condition. It means even if I study hard, I may not get a good score. But if I get a good score, it means I studied hard.
So to increase the economy by 40% is a bare minimum requirement, but doing so doesn't warrant its stability.
Hope it helps.

regards,
Arup Sarkar

Thanks for the explanation, now I got it.

Reworded stem: GNP must increase by 20% to avoid economic collapse. if the 20% threshold is reached, then a 40% is possible

if 40 % is impossible then 20% is not reached which in turn says economy will collapse. Hence Option B

20% is not achievable, then economy will collapse. That is the only statement that is definite enough to make a judgement.
If 20% is achieved, then 40% is achievable

If a 40% is not achievable, doesn't mean that a 20% is not achievable.


I think the answer should be C.

As posted in my comment,

From the statement, we can sum up that for no economic loss to happen 20% needs to be achieved. If 20% is achievable then a 40% is achievable.
It does not mean that if 40% is not achievable, then 20% is not achievable and hence the economy might collapse. For all you know a 30% could have been achievable.
The answer seems to be incorrect.

This question does not seem to be properly framed. Option B is obviously correct since achievability of 40% implies achievability of 20%. But option C will not be incorrect unless It says "only if". In the current format 40% acts as a sufficient but not necessary condition which is true according to the passage. It needs to be a necessary condition to be an incorrect choice.


In essence, option B and C are correct according to the given structure, but option C is likely intended to be wrong but turned out right due to a logical error.

For more details on necessary but not sufficient conditions, try this article:

https://e-gmat.com/blogs/gmat-critical-reasoning-necessary-vs-sufficient-conditions/

The way I interpreted the structure of the passage and answer C.... for better or worse.....

If Russia’s GNP Increases by 40% (or 20%), it does NOT necessarily mean that the economy will avoid collapse.

As written, the passage states:

IF the economy does NOT collapse —-> then one of the things that must have happened was that the GNP increased by 20% (there may be other requirements as well, but we can be sure this requirement was met if the economy did NOT collapse)

And we are told that if the 20% increase has occurred, then the 40% increase is achievable.


However, just because we achieved the 40% increase (and 20% increase), this does not mean that it is “impossible” for the economy to collapse. We can not say based only on 1 pre-requirement being met (20% increase) that the economy “will NOT collapse.”

There may be other requirements that need to be met to avoid collapse.

If you are following the Power Score Book, I believe they call this a “Mistaken Reversal.” Just because the necessary condition occurred does not NECESSARILY mean the Sufficient condition occurred.

We just know that in order to avoid economic collapse ——-> we must at the very least meet the 1 pre-requirement of the “20% increase”.

This is why I believe C is wrong.

Below is why I believe B is the correct answer.

Again, if you’re following the Power Score Book, the author’s refer to this as the Contrapositive.

If we can NOT meet the pre-requirement of the 20% increase (shown by the fact that we can’t get the 40% increase, which is achievable once we get the 20% increase) ——> then we can NOT avoid collapse. 1 of the requirements necessary to avoid the economic collapse has not been met.

If we can NOT avoid the economic collapse, then the collapse will occur.


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Without trying to go too far afield with all the “if-then” logic that makes my brain spin.....

There could be a million other things that Russia might need to do in order to avoid economic collapse.

We are only told in the passage about 1 of these requirements. To avoid collapse, Russia definitely has to get the 20% increase.

However, there still may be other requirements that must be met in order for Russia to avoid collapse.

Russia might hit the 20% and 40% increases and its economy STILL collapses because we are not told that the increase is the ONLY requirement that needs to be fulfilled to avoid collapse.

This is why we can not infer E with 100% certainty. If Russia collapses, it could be because of some reason not mentioned in the passage. Russia can still collapse even if the country meets the Percent Increase requirement.

The facts tell us that Russia needs the 20% increase in order to avoid collapse.

The facts do NOT tell us if this is the ONLY required thing that Russia needs to do in order to avoid collapse.


The question is testing the formal logic concepts behind Sufficient and Necessary Conditions. It is a topic that is much more common on the LSAT than on the GMAT.

If Russia has NOT collapsed ———-> then we know for sure that Russia, at the very least, met the % Increase requirement.

However if Russia DID collapse ———-> Russia still might have met the %increase requirement and some other reason caused the economy to collapse (maybe the Russian Mafia pulled off a monumental heist on all the government banks).


Lastly, the question source is Nova Prep. The company sometimes creates problems that are harder than the actual GMAT questions in order to challenge you.

I believe that you can get through the GMAT and get an awesome Verbal score without ever delving too deeply into Sufficient/Necessary Conditions. However, it’s just my opinion and others probably disagree with me.

Hope some of what I wrote helped at least a little??? If you want to read more about Sufficient/Necessary Conditions and Must Be True Questions, Power Score’s Critical Reasoning Bible is a great source.




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