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In the last decade, the country of Alumba has undergone a massive cons

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In the last decade, the country of Alumba has undergone a massive cons  [#permalink]

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New post 15 Jan 2018, 05:42
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In the last decade, the country of Alumba has undergone a massive construction boom. In one city, Semanta, hundreds of new buildings have been erected and, as a result, the ambient light at night has increased from 0.10 lux to 10 lux, causing migratory birds flying to alter their traditional path and fly into Semanta, where they often crash into buildings. The mayor believes that to ensure the birds keep to their traditional flight path while flying through Alumba, the city should turn off lights throughout the city at night during the bird’s migratory season, so that ambient light is around 0.10 lux.

Which of the following, is necessary, to evaluate the mayor’s proposal for limiting the amount of night light that Semanta emits?

A The amount of lux necessary to interfere with a bird’s navigational abilities.
B The percent of birds flying through Alumba that are drawn to Semanta’s night light.
C Whether the period in which birds migrate is consistent each year.
D Whether there are any other migratory birds flying through Alumba.
E Whether there are any other cities in Alumba that might also emit enough ambient light to confuse migrating birds.
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Re: In the last decade, the country of Alumba has undergone a massive cons  [#permalink]

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New post 15 Jan 2018, 06:01
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In the last decade, the country of Alumba has undergone a massive construction boom. In one city, Semanta, hundreds of new buildings have been erected and, as a result, the ambient light at night has increased from 0.10 lux to 10 lux, causing migratory birds flying to alter their traditional path and fly into Semanta, where they often crash into buildings. The mayor believes that to ensure the birds keep to their traditional flight path while flying through Alumba, the city should turn off lights throughout the city at night during the bird’s migratory season, so that ambient light is around 0.10 lux.

Which of the following, is necessary, to evaluate the mayor’s proposal for limiting the amount of night light that Semanta emits?

A The amount of lux necessary to interfere with a bird’s navigational abilities.
It is already given that earlier emission of 0.10 was not a problem, so getting it back to 0.1 should not be an issue

B The percent of birds flying through Alumba that are drawn to Semanta’s night light.
The issue is of amount of lux and not the number of migratory birds.

C Whether the period in which birds migrate is consistent each year.
Same as B

D Whether there are any other migratory birds flying through Alumba.
This does not affect the migratory bird in question

E Whether there are any other cities in Alumba that might also emit enough ambient light to confuse migrating birds.
Correct.. The conclusion is of the migratory birds in the country of Alumba whereas the argument talks of only Semanta"s night light..
If there is a excess of the light in other areas, it will effect the migratory birds of Albuma


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Re: In the last decade, the country of Alumba has undergone a massive cons  [#permalink]

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New post 15 Jan 2018, 09:20
NOT A.We are not bothered about the necessary lux for bird disturbance.The plan tells us that we are coming down to 0.1lux which dint create a problem before.Hence not this option.

E mentions the gap in the argument.
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In the last decade, the country of Alumba has undergone a massive cons  [#permalink]

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New post 02 May 2018, 17:46

Official explanation:



Premise #1: Birds flying through Alumba change their traditional migrating route because the light from Semanta confuses them and they fly towards Semanta.

Premise #2: The increase in lux accounts for this phenomenon.

Conclusion: Therefore, reduce night light during the bird’s migratory season so the bird does not alter its flight path through Alumba.

(A) is one of those answer choices that seems to be doing something. Indeed, you could make the argument that if the bird was drawn to Semanta before the construction boom but it didn’t crash into buildings (there weren’t too many), then reducing the lux back to .10 lux shouldn’t have an effect. Yet, this line of reasoning contradicts one of the main premises, that the increase in ambient light caused birds to “alter their traditional path”.

(B) Just because every bird doesn’t alter its flight path and fly to Semanta doesn’t determine whether the plan will be successful. Say only 20% of birds fly to Semanta. If the mayor’s plan saves those birds, it is effective. The conclusion is only focused on the birds that alter their traditional path.

(C) could be tempting if the conclusion didn’t mention “migratory season”. However, the mayor plans to turn the night lights down only during the migratory season, not during a set time of year. So it doesn’t matter whether the migratory season happens during the exact time frame each year.

(D) The existence of other birds does not relate to the mayor’s plan.

(E) The conclusion states that the mayor’s plan will ensure that the bird sticks to its traditional flight path as it flies through Alumba. But if there are other cities in Alumba also emitting light (remember the recent construction boom in Alumba), then the mayor’s plan will not be successful. True, birds might not fly into Semanta, but other cities will cause them to alter their traditional flight path and such a result goes against the conclusion.

Imagine, for instance, that a city after Semanata, along the bird’s route, emits 15 lux at night. Then, it doesn’t matter whether Semanata has turned its lights off, since some birds will be confused by the night light of this other city.



FAQ: I still feel like A is the best answer. Why isn't A correct?

The passage tells us that the reason why birds have started coming to the city (interfering with their navigational abilities) is because of the increase in lux above .10. So, from the information we're given, we have to accept that the reason why the birds have started altering their traditional flight path is because the lux increased above .10.Therefore, if the lux is reduced back to .10, logically the birds shouldn't have any more navigational problem.

That is, unless there is another city that has lux above .10. This is the point that (E) raises, and that's why it's correct.

To elaborate a bit more on (A) -- (A) gives us two options:

It turns out that the maximum lux that won't interfere with the birds is higher than .10 (but lower than 10). Well, that doesn't matter -- the plan will still work.
It turns out that .10 will still interfere with the birds --> This would directly contradict the information stated in the passage: we can't assume that this is the case without more information, which we're not given here.
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In the last decade, the country of Alumba has undergone a massive cons &nbs [#permalink] 02 May 2018, 17:46
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