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The passage gives us 4 facts.
1. Low-quality coal < High-quality coal (Cost)
2. Low-quality coal > High-quality coal (Required to generate the same amount of energy)
3. Low-quality coal > High-quality coal (Ash produced after burning)
4. Ash disposal is becoming more and more expensive
We can always simplify a CR inference passage into a set of facts.
Elimination on the basis of outside information or false statements.
Now, based on these facts - let us eliminate answer choices that don't follow:
(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.
Because you spend less on purchasing low-quality coal, the natural assumption could be that it is the most economically viable solution. But, consider that low-quality coal is less effective than the alternative, which means that the amount saved up-front per ton might actually be smaller than the extra amount that you need to spend in purchasing a larger quantity of low-quality coal, plus the money you need to spend in disposing of the larger amount of ash generated. Valid.
Mathematical Explanation:
LQ coal = Cost per ton (L) x Number of tonnes (Q) + Ash disposal cost (AC) x Amount of Ash (AA)
HQ coal = Cost per ton (H) x Number of tonnes (q) + Ash disposal cost (AC) x Amount of Ash (aa)
here, L<H; Q>q; AA>aa
Because we don't know the magnitude of the difference, we cannot conclusively say which type of coal will be an economically smart buy. Which is what (A) says, hence, we can keep A.
(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.
Even when the cost of ash disposal is 0 (fact 3 is no longer a determining factor), facts 1 and 2 will still mean that we cannot conclusively say which type of coal will be more expensive to use. Reject.
(C) Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
Simple translation -> (Transport cost (TC) / Total purchase cost) is greater for HQ coal than for LQ coal. But think about it, the transportation company wouldn't care about the quality of coal it is transporting, only the quantity.
Meaning that TC is the same for both, and since we know that HQ coal is more expensive, the (TC/Cost of 1 ton HQ coal) factor will have a larger denominator and the same numerator as the same ratio for LQ coal.
Hence, the ratio will actually be greater for LQ coal than for HQ coal. Reject.
(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 have absolutely no idea if the quality of coal burnt affects the generated ash in any way. Only the quantity changes, but in this case the quantity is 1 ton for both, hence we cannot say for certain based on the given facts if this is statement is true or not. REJECT.
(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.
What does least expensive mean? 10 , 10 , 10 , 9.9 , 10 - in this series, 9.9 is the least number. But if the cost of ash disposal is lower by 1% in a certain area, can we really say that all mining efforts will move towards LQ coal?
What about the 2nd fact? We might end up needing to spend more than HQ coal for LQ coal even if Ash (fact 3) disposal is taken out of the picture.
Cannot be inferred without outside information. REJECT.
_________________________________
Aakkash Singh | V90 Tutor
Check out www.centprep.com | Affordable & High Quality Verbal Learning
1. Low-quality coal < High-quality coal (Cost)
2. Low-quality coal > High-quality coal (Required to generate the same amount of energy)
3. Low-quality coal > High-quality coal (Ash produced after burning)
4. Ash disposal is becoming more and more expensive
We can always simplify a CR inference passage into a set of facts.
Elimination on the basis of outside information or false statements.
Now, based on these facts - let us eliminate answer choices that don't follow:
(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.
Because you spend less on purchasing low-quality coal, the natural assumption could be that it is the most economically viable solution. But, consider that low-quality coal is less effective than the alternative, which means that the amount saved up-front per ton might actually be smaller than the extra amount that you need to spend in purchasing a larger quantity of low-quality coal, plus the money you need to spend in disposing of the larger amount of ash generated. Valid.
Mathematical Explanation:
LQ coal = Cost per ton (L) x Number of tonnes (Q) + Ash disposal cost (AC) x Amount of Ash (AA)
HQ coal = Cost per ton (H) x Number of tonnes (q) + Ash disposal cost (AC) x Amount of Ash (aa)
here, L<H; Q>q; AA>aa
Because we don't know the magnitude of the difference, we cannot conclusively say which type of coal will be an economically smart buy. Which is what (A) says, hence, we can keep A.
(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.
Even when the cost of ash disposal is 0 (fact 3 is no longer a determining factor), facts 1 and 2 will still mean that we cannot conclusively say which type of coal will be more expensive to use. Reject.
(C) Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
Simple translation -> (Transport cost (TC) / Total purchase cost) is greater for HQ coal than for LQ coal. But think about it, the transportation company wouldn't care about the quality of coal it is transporting, only the quantity.
Meaning that TC is the same for both, and since we know that HQ coal is more expensive, the (TC/Cost of 1 ton HQ coal) factor will have a larger denominator and the same numerator as the same ratio for LQ coal.
Hence, the ratio will actually be greater for LQ coal than for HQ coal. Reject.
(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 have absolutely no idea if the quality of coal burnt affects the generated ash in any way. Only the quantity changes, but in this case the quantity is 1 ton for both, hence we cannot say for certain based on the given facts if this is statement is true or not. REJECT.
(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.
What does least expensive mean? 10 , 10 , 10 , 9.9 , 10 - in this series, 9.9 is the least number. But if the cost of ash disposal is lower by 1% in a certain area, can we really say that all mining efforts will move towards LQ coal?
What about the 2nd fact? We might end up needing to spend more than HQ coal for LQ coal even if Ash (fact 3) disposal is taken out of the picture.
Cannot be inferred without outside information. REJECT.
_________________________________
Aakkash Singh | V90 Tutor
Check out www.centprep.com | Affordable & High Quality Verbal Learning
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