#24 - Each December 31 in Country Q, a tally is made of the

[Administrator]

Complete Question Explanation

Must Be True. The correct answer choice is (B)

The stimulus consists of information about coal in Country Q.

First, we find out that at the end of each year, a tally is made of Country Q's available coal supplies, which are defined as the amount of coal that has been mined but not consumed.

It is very important that you interpret that statement correctly. The tally does NOT refer to the amount mined that year minus the amount consumed that year. What the tally refers to is the amount of coal, total, that the country has left over after consumption. That means that the tally incorporates the "roll-over" from the previous years. Most people who have trouble with this question have misread that sentence.

Second, we learn that the tally in Country Q is lower in 1991 than it was in 1990, and that Country Q does not get its coal from anywhere else, or export any coal.

If you misunderstood the first statement, it would be impossible to infer anything definite from the stimulus. However, once you understand that the tally is a running tally, we know that if it has decreased from 1990 to 1991, it must be true that Country Q is cutting into its reserves. In 1991, it consumed more than it produced.

Answer choice (A): Once you understand that the year-to-year comparison is irrelevant, you can eliminate this choice easily. If you misread the first sentence, you should still have eliminated this choice. Even if you thought that the tally only took into account coal mined and consumed in a specific year, it would be impossible to say why the tally was higher in one year, because either production or consumption could account for the change.

Answer choice (B): This is the correct answer choice. A correct reading of the stimulus indicates that in the year 1991, Country Q cut into its reserves, so that means more coal was consumed than was produced in 1991.

Answer choice (C): This answer choice is wrong for the same reason that answer choice (A) is wrong. You should realize that under the incorrect reading of the stimulus, either of these choices could explain the situation, but neither of them Must Be True.

Answer choice (D): This choice is wrong, because you should not assume that production necessarily remained constant. Remember, under any reading, it is the relationship of production to consumption that changes, and we are not certain individually how the two have changed. For example, consumption could have decreased, while production decreased more. Or, production could increase, while consumption increases more. And there are more options still, so this choice is no good for a Must Be True question.

Answer choice (E): There is absolutely nothing to indicate we ought to compare halves of years, and this choice is incorrect.

[FrannieVargas]

Logical Reasoning Must Be True and Main Point Question Set: I've read the online explanations to #26(pg 1-83) but still don't understand why the corresponding correct answer is correct.

#26-How are we suppose to know to take roll over into consideration? How can I prevent this misunderstanding in future questions?

ADDITIONALLY, when I was doing this problem set I found that most of the questions I answered incorrectly were Must Be True Questions where the stimulus was a fact pattern( 6 out of the 8 I got wrong). How can I better equip myself to answer these types of questions? What should I pay attention to? What should I be looking for?

Thank you! I hope to year from you soon.

Loyally,
Frannie Vargas

[Nikki Siclunov]

In question 26, Total Coal Supply = Coal Mined minus Coal Consumed during the year. If, on 12/31/91, the Total Coal Supply was lower than it was on 12/31/90, then clearly there must have been negative growth in the amount of coal during 1991. In other words, the country consumed more coal than it mined that year.

Think of it in a different context: let's say you have $10K in your checking account on 12/31/2010, but only $9K on 12/31/2011. You must have spent more than you made in 2011. It doesn't matter how much you made/spent in previous years: the only thing that would affect the difference in your checking account between the two dates is what happened in 2011.

Whenever you have a fact pattern to deal with, make sure you fully understand the facts and prephrase a conclusion that a reasonable person would draw based on these facts. In most of these questions, they will test your ability to put the facts together and figure out what can be concluded from them.

[ellenb]

Dear Powerscore,

I totally got confused with the Tally here, how they calculate it? Still seems confusing. I have read the explanation. But I am kind of getting it, but I want to make sure that I do not get into future traps such as this. What are simmilar questions that could be to this? what is the mistake that I made? because I totally thought that tally is amount that has been mined -amount consumed: I thought tally to be the left over (however I understand it to be commulative remains from last years too) where did it say that? did I read it too fast or what is the word that can help me understand that it is commulative based on previous years and not just one year?

Thanks

Ellen

[Nikki Siclunov]

Hi Ellen,

The definition of "total available coal supplies" is presented in the first sentence of the stimulus: the total amount of coal mined throughout the country but not consumed. Since the author does not limit this calculation to one particular year, we can assume that the tally will take into account any supplies left over from previous years. Indeed, the fact that the tally represents the "total available coal supplies" means just that: when you draw the bottom line on 12/31, how much coal do we have in total?

Let's use an analogy: every December, you look at your bank account to see how much money you have (your "total savings," if you will). Your savings will be a function of how much money you made minus how much you've spent. The savings won't reflect only the amount you made vs. spent in 2012, but in the aggregate up to this point. So if on 12/31/2012 you have less money in your account than in 12/31/2011, the only conclusion you can draw is that you spent more money than you made in 2012.

This is a stimulus using numerical evidence. Check out the HW for Lesson 9 - you will find many questions similar to this one there.

Hope this helps!

[ellenb]

Dear Powerscore,

I did this question again and I totally caught myself doing the same mistake, misinterpreting the total amount, is there something I can do for the future if I encounter questions like this? Nikki mentioned Chapter 9, which exact questions have examples like this?

Or could you give me some examples which use the same logic as in this scenario, but in LSAT context?

Thanks,

Ellen

[Steve Stein]

Hi Ellen,
Part of what makes this question so difficult is that the author discusses the total amount of coal that has been mined but not used--not the net yield from one particular year.
Unfortunately you won't likely see other examples of this concept on every test(actually that might be fortunate!), although I could see a related idea applied to a question about a given region's population, for example, in which the birth rate and death rate work in different directions to affect the running total population. The same could work with immigration rates vs. emigration rates in a particular country. The recurring theme, again, the idea is a running tally, with increases and decreases that affect the running total.

I hope that's somewhat helpful! Please let me know whether that answers your question--thanks!

~Steve

[rameday]

For question 26 on page 1-83 I don't understand why B is right and why A and D are wrong. I thought initially upon reading that we knew nothing based on the stimulus as to how much coal had been consumed in 1991 only how much had been mined. So that led me to eliminate answer choice B,C,D,E.


A

[KelseyWoods]

Hi A,

The first statement in this stimulus is what often gives people trouble. It's deceptively tricky. What it tells us is that Country Q makes a tally of the total available coal supplies at the end of each year. That tally is NOT the amount mined minus the amount consumed. It's basically just how much coal they have on hand.

Let me give you an analogy. As an LSAT instructor, I carry a lot of pencils and I tend to lose them or give them away so I often need to buy more. Let's say I tally my pencil stock at the end of each year. At the end of 2012, I had 10 pencils. At the end of 2013, I had 4 pencils. Based on these facts, you really don't know anything about the specific amount of pencils I bought or lost in either year. All you know is that at the end of 2013, I had fewer pencils than I had in 2012. Maybe I didn't buy any pencils in 2013 but I lost 6 and that's why I'm only left with 4. Or maybe I bought 500 pencils in 2013 and I lost 506 of them and that's why I'm only left with 4. You have no idea. But what you do know is that I lost more than I bought in 2013 because I ended up with fewer pencils by the end of the year than I had at the start.

That same concept holds true here. We don't know specifically how much coal Country Q mined or consumed in 1991. We can't make any comparisons between 1991 and 1990 in terms of how much coal was mined and consumed in each year (which is what both answer choice (A) and (D) do). But we can say that if Country Q has less coal at the end of 1991 than it had at the start of 1991, they must have consumed more coal than they mined.

The "tally" concept is really what makes this a tricky concept. But once you figure out what that means, it isn't so bad

Hope this helps!

Best,
Kelsey

[reop6780]

The correct answer is B while i chose D.

I did not think answer B must be correct because even though the amount of coal consumed in 1991 was NOT greater than the amount of coal mined in 1991, "(total amount of coal mined) - (coal consumed)" can be still lower in 1991 than 1990.

For example,

1991: amount mined - 100
amount consumed - 90

(coal consumed is NOT greater than coal mined in 1991)

1990: amount mined - 150
amount consumed - 90

1991 (100-90) is still lower than 1990 (150-90).

This question was perplexing for me since the amount of supply (mined) and demand (consumed) can either increase or decrease each year.

Is the last sentence of not importing nor exporting coal since 1970 limiting any condition of supply and demand?

( I thought w/o import or export, the domestic supply and demand can vary anytime)