Twenty years ago, Balzania put in place regulations requiring operator

As tagged above, it is a 700 level question. It is certainly one of the hard ones though not ambiguous at all.

Hi Karishma,
Is it really difficultwhen one looks at the answer choices..
all the choices are out of context other than the answer..
the Q tells us that reclamation cosst has gone down without any improvement in tech...

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country.
out of context as we are not comparing different countries
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years.
again use has nothing to do with reclamation cost.. out of context
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.correct
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.
Again we are not comparing cost between two different methods of mining... out of context
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.
it again speaks of usage , which has nothing to do with reclamation cost per ton of coal

Dear chetan2u and kobaum,
I'm happy to respond on this issue. With all due respect to Karishma, for whom I have considerable respect, I am going to introduce a different perspective. I am going to say that I am deeply skeptical of this entire idea of a "700 level question." Yes, on average, there are harder questions and easier questions. Nevertheless, the idea that we can pinpoint with mathematical precision the difficulty of any individual question is ludicrous. See this blog article:
https://magoosh.com/gmat/2014/is-this-a- ... -question/
Any reasonably challenging question is going to be harder for some folks and easier for some folks. Even if the idea of quantifiable difficulty has some reality, it is only in the broadest statistical sense, and not at all in the individual perception of the question. The fact that one isolated student finds a question easy or hard means absolutely nothing about the objective difficulty of the question. You see, students are convinced of this fiction that all questions have an objective, quantifiable difficulty; then GC, trying to accommodate students, creates this tag; then we folks who write questions and post them on GMAT club have to use that tag on a question we are posting. To be honest, once I write a GMAT practice question, I usually only have a vague guess about how easy or hard it is, and some times, as we gather data on questions, I find that my guesses were wrong. I am going to say, my friends, that it is a complete waste of time to obsess about whether this question or that question is a mythical 700 level question. Forget all the numbers, forget all the scoring, and keep practicing & learning & challenging yourself. You waste valuable time and energy when you focus on what doesn't matter. Focus on understanding as many questions as possible, and in particular, focus on understanding your mistakes and how to learn from them. Focus on understanding more deeply what is difficult for you. Forget about whether that question is this level or that level.

Does all this make sense?
Mike

Fact 1: Reclamation technology has not improved.

Missing information: But mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.

Fact 2: So, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

This is a tough one. Awaiting OA.

Premise 1: Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land.
Premise 2:Since then, reclamation technology has not improved.

Conclusion: Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country. -We are not worried about the other countries' condition.
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years. -Correct. If the demand reduces, then the supply also follows the same trend. Thus, the production of coal reduces thereby reducing the reclamation cost.
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. -Okay. This is a fact set. A person might give up on the land or not.
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines. -Out of scope
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines. -Out of scope. Doesn't talk about the cost involved.

IMO its E.
Now there is greater percentage of coal mined, so coal quantity has increased.
Eventually, the per ton coal cost will reduce.

I think it's C.

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country. - Don't care about what is happening in other countries. Not relevant.

B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years. - Not relevant. Use of coal has nothing to do with reclamation cost of the surface mines. Coal could still be heavily used, just not as a fuel. It still does not explain the lower reclamation cost compared to 20 years ago, especially since the tech has not changed.

C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. -This explains why the reclamation costs could have gone down even though the reclamation technology hasn't improved. It is generally easier to level, say a ditch,on a leveled surface compared to that on a slope. So mine operators started mining on more leveled surface mines v/s mountainous areas - therefore lower reclamation costs.

D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.- Not relevant.

E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines. - Surface mines could be situated anywhere. This does not tell us anything about why the costs could have gone lower. Not relevant.

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country. Out of scope! OUT
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years. Then the cost might have gone up, contradicts! OUT
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. Something changed from the past practice, and decreased the cost! Probable - Keep
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines. No reason why the cost dropped now! OUT
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines. But at what cost? OUT

Please provide Kudos!

IMO

Surface mining + Underground mining = Total coal that the mine produced

Reclamation cost comes from only surface mining (as it destroys land surface)

So Average reclamation cost (for a surface coal mine being reclaimed today) per ton of coal that the mine produced is based on
Surface/(Surface+Underground)

Only way for the average to be reduced is to decrease in mix (percentage) of Surface mining or it's a increase in mix of Underground mining

Look at the answer choices, Only C. and E. say about the mix of coal production

But E. is telling that the mix of Surface is increased hence it's opposite to what we are looking for as this will increase the average reclamation cost

While C. is implying that the mix of Surface is decreased (or that of Underground is increased) as it's telling that "Mine operators have generally ceased surface mining in the mountainous areas of Balzania"
(The cease is only in mountainous areas (means that other areas of Balzania still have surface mining), that's why there is still reclamation cost. If the cease is for all areas, there will be no reclamation cost as it's no more surface mining in Balzania)

Actually, we can plug some numbers to test this...

"reclamation technology has not improved" is just there to have the cost of reclamation per area of land unchanged thus leave the mix as only factor

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country. (Not about other countries)
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years. (Not about Coal as fuel - out of scope)
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. Looks kind of OK for now...
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines. ( Could be but underground mine - off topic)
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines. Hmm C & E?

GMAT is producing quite a few spurious answers so even if C is the answer - E makes the most sense
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. Looks kind of OK for now...
1st bringing in outside off topic mountainous areas is confusing - HR kind of stuff - so alarm bells should start ringing - lets dig into the real numbers to assess the situation then - Avg Surface CM hmm Total Cost/ No then - but they are saying they completely ceased - no activity - zilch - so that number can never be 4 - if anything that number is an undefined off shoot number just like the dreams of the mountainous areas...But still we will think about it and go to the real BIG E which is screaming out - hey look at me - I really really look good
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.
Even this has anomalies - but then is it HR or being precise sticks to a point? Just what CR wants - Lets check it out -
Avg Surface CM cost- = Total Cost/ Number = so number as defined by percentage comes from SM - We no nothing about total cost - but whatever it is High or low it must be a defined number - given this situation the number could definitely vary between 4 and 8 or even stay the same for that matter - but given there is a number stated "only 4 less than half - so 8+/- 2 - previously - should this not be the answer?

Wait C is still beckoning to me with undefined out of scope **** - clocks ticking - tick tock - nah C - you no good - too much blah/out of scope +HR+undefined number - its like glaring mess of muddy puddle- I need some specifics here - go with E

But then just like my other post today - GMAT glitch kicks in full throttle - I ask are these very recent - nope post goes back to 2004 - so this messy puddle has been going around since - that's a real surprise

Happy to get some rebuttals here - how to make undefined numbers definable - GMAT magic?
Cumberbatch as in Sherlock might soon get to the bottom of this ...if Moriarty is not doing tick tock tick tock behind him...

Explanation of a similar question from Ron Purewal:

https://www.dailymotion.com/video/xlz7ht#.UTKMQXx8KlY

if the overall reclamation costs have gone down, doesn't that mean the average reclamation cost will also go down?

Hi avigutman - just wanted to focus only on the word "Average reclamation cost" ... To calculate the average, It must be

Average reclamation cost for Surface Mine A
== Total reclamation cost incurred by Surface Mine A / Total coal produced by surface mine A

Question : in the Numerator above, is the total reclamation cost a fixed fee or a variable fee ?

My understanding is it we don't know

Hence if the
-- denominator in the formula above reduces, the numerator maybe stays the same (implying, numerator is a Fixed cost)
-- denominator in the formula above reduces,, the numerator reduces (implying, numerator is a variable cost)

Given we don't know if the Numerator is a fixed cost or a variable cost -- any changes in the denominator (increase or decrease) may or may not change the overall average

This is what option B and option E are doing

Option B is saying the denominator increases whereas option E is saying the denominator decreases. But given we don't know if the numerator stays fixed OR if numerator decreases as well -- we can't really tell if the Average will increase / decrease or stay the same

Hence option B and Option E are out of scope

You’re correct that the denominator is Total coal produced by surface mine A
However, I don’t see how choices B and E are talking about that.

Posted from my mobile device

Hi avigutman - thank you so much for responding ...hmm i thought option B certainly affected the denominator in my formula above

OR ARE YOU SAYING

Perhaps Coal as a fuel may have dropped in Balzania but Balzania is perhaps exporting more coal than before so the net effect on the amount being mined is net zero --- Is that why you say option B does not affect the denominator specifically ?

Option E -- is talking about a %. Perhaps surface mines are still mining the same amount whereas the underground mines are the one's that have reduced their mining numbers. Thereby surface coals automatically have a greater % of the pie even though surface mines are mining the same amount of coal as before.

Regarding B: There are several links in the chain connecting the use of coal as a fuel with the amount of coal mined from surface mines. What about other uses of coal? What about imported/exported coal? What about other coal mines (non-surface)?

Regarding E: yes, you got it.