Electric utilities pay less for low-quality coal per ton

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Electric utilities pay less for low-quality coal per ton delivered than for high-quality coal. Yet more low-quality coal than high-quality coal must be burned to generate the same amount of electricity. Moreover, per ton of coal burned, low-quality coal generates more ash than does high-quality coal, and the disposal of ash is becoming more and more expensive.
The considerations above, if true, most strongly support which of the following claims?

A. A coal-burning utility might not be assured of benefiting economically by always adhering to the policy of keeping its overall coal purchasing costs as low as possible.
B. In those regions where the cost of disposing of coal ash is negligible, it is more expensive for coal-burning utilities to use high-quality coal than low-quality coal.
C. Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
D. It is no less expensive to dispose of a ton of coal ash that results from the burning of high-quality coal than it is to dispose of a ton of coal ash that results from the burning of low-quality coal.
E. In regions where coal-ash disposal is the least expensive, reserves of low-quality coal are likely to decline at a faster rate than are reserves of high-quality coal.



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Please explain the reason for eliminating the options . I also need to know why "D" is wrong..thanks !

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by [email protected] » Sun Sep 29, 2013 11:42 am
Hi guerrero,

This is an example of an Inference question; these questions can sometimes be difficult, but this one is fairly straight-forward if you take good notes.

The facts:
-Low quality coal costs less per ton than high quality coal
-More low quality coal is needed (than high quality coal) to generate the same amount of electricity
-Low quality coal generates more ash than high quality coal
-Disposal of ash is becoming more and more expensive

We need an answer that logically follows from the above list (the correct answer might be based on any combination of the above facts). Before looking at the answers, the facts that stand out to me are the last two (low quality coal creates more ash AND disposal of ash is BECOMING MORE AND MORE EXPENSIVE).

Answer A addresses how keeping coal purchasing costs low (re: buying low quality coal) might not be a benefit economically (because of the coal ash expense and how it's increasing). This is a GREAT MATCH.

Answer B addresses specific regions, which the prompt doesn't address.

Answer C addresses transportation costs, which the prompt doesn't address.

Answer D doesn't mesh with the facts. We're NOT told if any particular type of coal ash is more/less/equal expensive to dispose of; we're only told that low quality coal generates MORE ash.

Answer E addresses coal reserves, which the prompt doesn't address.

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by vinay1983 » Thu Oct 03, 2013 3:48 am
guerrero wrote:Electric utilities pay less for low-quality coal per ton delivered than for high-quality coal. Yet more low-quality coal than high-quality coal must be burned to generate the same amount of electricity. Moreover, per ton of coal burned, low-quality coal generates more ash than does high-quality coal, and the disposal of ash is becoming more and more expensive.
The considerations above, if true, most strongly support which of the following claims?

A. A coal-burning utility might not be assured of benefiting economically by always adhering to the policy of keeping its overall coal purchasing costs as low as possible.
B. In those regions where the cost of disposing of coal ash is negligible, it is more expensive for coal-burning utilities to use high-quality coal than low-quality coal.
C. Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
D. It is no less expensive to dispose of a ton of coal ash that results from the burning of high-quality coal than it is to dispose of a ton of coal ash that results from the burning of low-quality coal.
E. In regions where coal-ash disposal is the least expensive, reserves of low-quality coal are likely to decline at a faster rate than are reserves of high-quality coal.



Source - GMATPREP

Please explain the reason for eliminating the options . I also need to know why "D" is wrong..thanks !

OAA
Prompt says

Low quality coal===low cost
High quality coal===High cost

More amount of low quality coal is needed to generate power than the amount of high quality coal needed.

Low quality cooal produces more ash than what high quality coal produces
Ash disposal is getting costlier

So we can infer here that just by buying low quality coal we cannot reduce our costs. The option that is similar to this will be the correct one

Option A===Bingo!

B==Are we told anything about how much it cots to dispose ash?maybe then we could have considered this option

C===Irrelevant

D==Trap choice according to me. But still do we care about costs of disposal of ash produced from low quality coal and high quality coal. Even if we consider it to be true, so what?What next?Can we do something now. No

E===Irrelevant and not known to us

A is the best choice, which is as close as possible to the paraphrased prompt


Rich by the way is bang on!(as always)
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!

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by ceilidh.erickson » Fri Oct 04, 2013 11:55 am
When you're answering a DRAW CONCLUSION / INFERENCE question, the most important thing to ask yourself is WHAT MUST BE TRUE?

In this argument, we're given:
LQC costs less per ton than HQC... but we don't know how much less
more LQC must be burned than HQC... but we don't know how much more
LQC generates more ash (which costs $) than HQC... but you guessed it, we don't know how much more

Can we say for certain that HQC is a better investment? Or that LQC is? No, because we don't have any information about RELATIVE difference in costs or amounts.

When you're going through the answer choices, eliminate anything that MIGHT NOT be true!

A. A coal-burning utility might not be assured of benefiting economically by always adhering to the policy of keeping its overall coal purchasing costs as low as possible.
We LOVE the phrase "might not" on draw conclusion questions! It's really hard to prove that wrong. This says exactly what we deduced - we don't really know which one is more cost-effective.

B. In those regions where the cost of disposing of coal ash is negligible, it is more expensive for coal-burning utilities to use high-quality coal than low-quality coal.
We don't know that it's definitely more expensive, because we don't know about relative amounts of coal needed.

C. Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
Does this have to be true? Not necessarily.

D. It is no less expensive to dispose of a ton of coal ash that results from the burning of high-quality coal than it is to dispose of a ton of coal ash that results from the burning of low-quality coal.
We aren't given any information about disposal costs PER TON. All we're told is that LQC produces a greater AMOUNT of ash. We can't know if this is true.

E. In regions where coal-ash disposal is the least expensive, reserves of low-quality coal are likely to decline at a faster rate than are reserves of high-quality coal.
We're not given any information about different behaviors in different regions. This isn't necessarily true.


When you're going through the answer choices, focus on DEALBREAKER LANGUAGE!
Wrong answers will often have definitive/extreme language: it must be, only, cannot, etc
Right answers will usually have softening, qualifying, hedging-our-bets language: might be, some, likely, probably, perhaps
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Harvard Graduate School of Education

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by ceilidh.erickson » Fri Oct 04, 2013 11:57 am
For more on avoiding dealbreakers in draw conclusion/inference questions, see: https://www.beatthegmat.com/bone-depleti ... tml#569967
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education