Q24 - Each December 31 in Country Q

[linzru86]

The answer is B, but I don't see how one can come to a conclusion like that. B makes a comparison between coal consumed and coal mined in just the one year, 1991, what am I missing here?

[ManhattanPrepLSAT2]

This is an inference question, so what we want to do is select the answer that is most provable based on the information given. Please keep in mind that the right answer does not have to represent the "main point" of the argument given.

Let's break down what the argument says:

At the end of each year, a tally is taken, and that tally = all coal mined - all coal consumed.

We're told that the tally was lower after 1991 than it was after 1990. That means that during 1991, more was consumed than mined. This is what (B) states.

Here's an analogy that might help -- imagine the tally to be like your bank balance --

Every month, you add income to your balance and subtract the money you spent. If you balance goes down after a particular month, you know you spent more during that month than you made.

[opulence2001]

I concluded that the tally T= M (amt mined) - C (amount consumed). For this question the question asks what must be true since T1991 is less than T1990.

I thought that this could be the result of M decreasing from 1990 amts or C increasing from 1990 amts or both. The question asks what must be true and the correct answer is B: It must be true that the 1991 amounts of C is greater than the 1991 amounts of M.

I'm not sure how this has to be true since it compares the amounts between the two years.

[bbirdwell]

This question is confusingly (poorly) worded, and thus choosing the correct answer is tough! The tally is first defined as the TOTAL amount of coal available, and that's the definition that (B) relies on, despite the fact that the hyphenated phrase says "the amount mined but not consumed."

So if we have X tons of coal at the end of 1990, they carry over to 1991, because that's our "total" available supply. And if we end up with less at the end of 1991 than we started with, that means that in 1991 we burned up more than we mined.

[nemeshb]

wow bbirdwell that cleared it up nicely. I didn't realize the supplies were being carried over each year, but knowing that really clarifies it. Why wouldn't they state that?! Isn't that a big assumption, or is that supposed to be obvious?

[mharr]

Great explanations, but I have the same question as nemeshb. I am wondering how we are supposed to realize that the total amount of coal remaining carries over to the next year? The question is not as difficult when that piece of information is known, but was very difficult for me to grasp when I did not know that piece of information.

[ohthatpatrick]

Yeah, I agree that the wording isn’t super friendly. I wouldn’t say the carryover idea is obvious, but it is a safe assumption to make.

At the beginning of every LR section it instructs us that we should not make any assumptions that are "by commonsense standards implausible, superfluous, or incompatible with the passage".

If I mined 50 tons of coal this year but only consumed 40 tons of coal, is that remaining 10 tons of coal still available to me next year? Presumably yes.

To make the opposite assumption, that the 10 tons of coal I didn’t use is now UNAVAILABLE to me seems like a superfluous or implausible assumption to me. It’s telling myself more of a story to make it seem like the leftover coal is unavailable. It’s a more conservative judgment to assume that the leftover coal is still available.

What scrambles our circuits on this problem is that so much of it is based on "what happened that year".

But the definition of "total available coal supplies" does NOT have anything to do with any specific year. It is defined timelessly as "the total amount of coal that has been mined throughout the country" (ever) minus the "the total amount consumed throughout that country" (ever).

Essentially, the yearly tally just tells us how much coal surplus we still have in Country Q.

Hope this helps.

[cwolfington]

This one was tough for me. I was looking for an answer that said either "Q mined less coal in 1991" or "Q consumed more coal in 1991", but these are answers A and C, respectively, so I knew they couldn't both be right.

Crossing them out, B becomes the only one that makes sense. But how can Q consume more coal than it mines if it doesn't import any? The inference is that the coal must carry over year to year, and the stimulus doesn't forbid this.

I wasn't comfortable with B at first, but it was the only one that made sense. The lesson I took from it was that the LSAT might demand inferences when you don't expect it.

[liujie.1644]

This is my thoughts, if it can help anyone.
T(90)=Total coal in 1990
T(91)=Total coal in 1991
C(90)=Coal consumed in 1990
C(91)=Coal consumed in 1991
M(91)=Coal mined in 1991

So, the text tells us this:
T(90)-C(90) >T(91)-C(91)
We also know that T(91)=T(90)-C(90)+M(91)
(Explanation: T(90)-C(90) is the Coal at the beginning of 1991, T(90)-C(90)+M(91) is the total Coal in 1991)
So, T(90)-C(90) >T(91)-C(91) means
T(90)-C(90) >T(90)-C(90)+M(91)-C(91), means
0>M(91)-C(91),
So, C(91)>M(91), which means Coal consumed in 1991 is greater than coal mined in 1991.

[jam3sd89]

To make the opposite assumption, that the 10 tons of coal I didn’t use is now UNAVAILABLE to me seems like a superfluous or implausible assumption to me. It’s telling myself more of a story to make it seem like the leftover coal is unavailable. It’s a more conservative judgment to assume that the leftover coal is still available.

Why would we need to make either assumption? It only says that this coal WASN'T consumed. No coulda, woulda, shouldas. Why would we assume it has anything to do with consumption whatsoever? They never said the coal was "leftovers" Why are we forced to assume that unconsumed coal is in any way related to consumed coal? They could be stockpiling coal for Santa, or maybe they're doomsday prepping.... now I know what you're saying... that it seems kind of ridiculous once we ARE forced to make an assumption. But I was under the impression that it wasn't our job to imagine an alternate purpose for the coal? It's overreaching. It's ASSUMING.

And anyway, your reasoning doesn't quite stand because whether it's AVAILABLE or UNAVAILABLE isn't relevant to our understanding of how the extra coal is accounted for. The way I understood it was that the two annual numbers were independent of each other. So for 1990 a surplus was created, and for 1991 another, smaller surplus of coal was created. This would mean that even if we assume the extra coal rolls over into the next year, it in no way indicates anything about the consumed coal numbers. the overall surplus of coal by the end of 1991 could be the combined amounts from '90 and '91, and perhaps other previous years.


They didn't specify and they did not link it to the consumption explicitly. It's a bogus problem.

[tommywallach]

Sorry, but it's really not. If I tell you about my surplus commodity for 2001, then my surplus commodity for 2002, the logical interpretation is that I've told you two separate numbers, not an aggregate number. If the 2002 number were an aggregate, I would've said so (because by this logic, we also wouldn't know the surplus from 2001, which could've been an aggregate of all previous years, etc.). None of these assumptions are unfair, because everyone knows what coal is. Coal is a resource, mined with the intention of being used, and it lasts a long time. None of these are unreasonable assumptions.

-t

[michellemyxu]

This is a really tough question... here are my thoughts after 15 minutes of struggle, if it helps with anyone:

X=supply

1990: X
1991: X + newly mined - consumed

1991 < 1990, meaning:
X + newly mined - consumed < X

newly mined < consumed

[MeganL677]

I see this as an iterated equation.
Don't be afraid.. it just looks terrifying but easy to understand.


Firstly, define:
(1)coal's Supply of a particular year= Remainder from the last year+ newly Mined this year.
(not so obvious, what I mean by "coal's Supply of a particular year" is the same as the "total available supply(TAS)" mentioned in the stimulus, which is: TAS= "has been mined"- C)
What inherently in the meaning of "has been mined" is that it includes the remainder from the past year and the newly Mined this year!
i.e.
S1990=R1989+M1990
S1991=R1990+M1991
......
(This is what I mean, iteration...)


(2) The Remainder of coal in a particular year= that year's coal's Supply- that year's Consumption. (obviously)
i.e.
R1990=S1990- C1990
R1991=S1991- C1991
......


We can see (1) and (2) have repeated terms. Combine the two equation we get:

R1990= (R1989+M1990)- C1990---------Equation1
R1991= (R1990+M1991)- C1991---------Equation2
....


If we only look at Equation 2, which have both R1991 and R1990, and you know what I'm going to do.
As indicated by the premise, R1991 was considerably smaller than R1990.
i.e. R1990-R1991>0
Shift the terms in Equation2, we get:
R1990-R1991= C1991- M1991>0

Thus we get our answer B, which simply says C1991- M1991>0.

What did I learn from this question?
I think what's really tricky about this question is that I didn't properly understand the phrase "has been mined" that it includes the remainder from the past year, and this omission led me to the wrong answer D.
It's never easy to see B immediately.



Hope this helps~

[AbhishekM843]

The way I see it, both A and B are accurate answers.
There are two ways that they end up having a lesser tally of coal in 1991 than in 1990.

The first way is that they ended up mining waaaay less coal in '91 than in '90. Even if you carry forward the surplus from '90, it is still possible to offset that surplus by just mining less that year than what they consumed for that year. Thus, A is correct.

The second way is that consumption went up, stipulating that production stayed constant. This way B would be correct.

For B to be the only correct answer, you would have to assume that production didn't go down in '91. Nowhere in the stimulus does it state that production was didn't decrease. Thus, A and B are both valid answers, and I just guessed between the two.