Gold is typically mined from two different types of geolo...

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OK, so i got this question today from the GMATPrep software. The question is as follows:
Prospect:
Gold is typically mined from two different types of geological formations (known as deposits): lode deposits and placer deposits. Lode deposits are what prospectors dream of finding: large deposits of nearly pure gold. Such deposits are located where they were originally deposited by the mineral-bearing solutions that carried the gold up from the earth's interior. Placer deposits, on the other hand, come from preexisting lode deposits that are exposed at the surface of the earth. These lode deposits' exposure to the weather causes gold to be released from surrounding rock and transported by rivers in the form of dust or flakes. When a stream carrying the gold slows, the gold collects in pockets of sand. Placer-deposite mines have historically been the source of approximately the source of 35% of the total gold mined in the US. However, in recent years, the quantity of gold mined from such deposits has decreased as the readily accesible deposits have been exhausted. Thus, despite an increase in net gold mined, placer-deposit mining now accounts for only a few percent of total gold mined in the US.

Environmental Scientist:
Because -unlike mining lode deposits- mining placer deposits does not usually involve crushing rocks and using chemicals to extract gold, the environmental impact are generally less than those of mining lode-deposits. The primary impacts of placer-deposits mining are habitat destruction and sediment release. Habitat destruction occurs as a result of river diversions and disruption of river bottoms and banks, and the large amount of silt and sediment released can severely impact water quality. Modern commercial operations tend to use settling ponds to prevent this discharge.
mining lode deposits has a much larger environmental impact by virtue of the size of such operations, the generation of waste material, and the use of toxic chemicals. The gold comes out of the ground as a raw ore -gold aggregated with other minerals. On average, such mining operations process approximately 130 kilograms of raw ore to produce 1 gram of pure gold. Unlike placer-deposits mines, modern commercial lode-deposit mines are massive operations, some displacing and processing up to 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day.

For which one of the following questions concerning the time the passages were written does the information provided supply the clearest answer?
a) How much raw ore did the average lode-deposit mine process daily?
b) What was the total annual quantity of pure gold produced globally by placer-deposit mines?
c) What were the principal forms of environmental damage attributable to chemicals used to extract gold from raw ore?
d) What were the principal forms of environmental damage attributable to mining placer deposits?
e) What was the total annual quantity of gold mined in the US?

Answer is D

Sincerely, I didn't even understand the question. I'd love some explanation on this question, and if someone knows this one should be an easy-medium-hard type of question.
Thanks a lot!

P

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by Marty Murray » Thu Aug 20, 2015 8:23 pm
petocities wrote:OK, so i got this question today from the GMATPrep software.

I'd love some explanation on this question, and if someone knows this one should be an easy-medium-hard type of question.
This question is close to being a very long version of a CR inference question. To get the right answer, we are looking for the question the answer to which is best supported by the information in the passages.

A thing that makes understanding the test question a little challenging is its saying, "concerning the time the passages were written". So the test question almost seems to be about a time period somehow, but actually what's going on is that "the time the passages were written" is mentioned just to make clear that the answer choice questions are referring to things going on at the time the passages were written.


For which one of the following questions concerning the time the passages were written does the information provided supply the clearest answer?

a) How much raw ore did the average lode-deposit mine process daily?

This is a trick question, because the second passage provides an average, the average amount of ore used to produce a gram of gold, and then goes on to say that some mines process a certain amount of raw ore daily. That second figure is not an average, however, but an example. So this question is not answered.

b) What was the total annual quantity of pure gold produced globally by placer-deposit mines?

There is no way by using the quantities discussed in the passages to arrive at the annual quantity of gold produced.

c) What were the principal forms of environmental damage attributable to chemicals used to extract gold from raw ore?

This damage is mentioned in the second passage, but the forms are not detailed.

d) What were the principal forms of environmental damage attributable to mining placer deposits?

This damage is discussed in detail. The second passage says, "The primary impacts of placer-deposits mining are habitat destruction and sediment release."

So this question is answered rather clearly.


e) What was the total annual quantity of gold mined in the US?

While the total quantity of gold mined annually is discussed at the end of the first passage, no actual quantity is mentioned.

So the only question to which a clear answer is provided by the passages is d.

I would call it a medium difficulty question, though from what I understand multi source reasoning questions tend to be higher value IR questions.
Marty Murray
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by petocities » Fri Aug 21, 2015 4:49 am
Thanks a bunch Marty.
My main problem with this question was the actual question. The wording of the question confused me, especially the bit of "the time the passages were written", so I missed the meaning of it.

Thanks a lot for the help, it's clear now where I erred.

Best!