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

[Lucas Moreau]

Hello, reop,

You got a little tangled up in your math, there. But it's fine. Questions like this can easily get confusing.

The trick is that total coal supplies decreased from 1990 to 1991. The statement about there being no imports or exports is to ensure that the only things affecting the coal supply are coal mined and coal used within Country Q. Let's do some numbers:

Total coal in 1990: 20,000 tons
Total coal in 1991: 10,000 tons

10,000 tons is "considerably lower" than 20,000 tons, I'd say! What this means is, combined with the statement of no imports or exports:

Total 1990 coal + total coal mined in 1991 - total coal consumed in 1991 > total 1991 coal

Adding in numbers:

20,000 + total coal mined in 1991 - total coal consumed in 1991 > 10,000

Simplifying:

Total coal mined in 1991 - total coal consumed in 1991 > -10,000

This means that the total coal consumed in 1991 must be greater than the total coal mined in 1991. Whether it's 10,000 tons or any number, the answer is the same. If the total coal consumed in 1991 was equal to or less than the total coal mined in 1991, then there wouldn't be less total coal supplies in 1991 than in 1990, which there were.

Hope that helps,
Lucas Moreau

[reop6780]

Hi, Lucas

I don't understand how you came up with such formula to begin with

"Total 1990 coal + total coal mined in 1991 - total coal consumed in 1991 > total 1991 coal"

Is this the correct way of expressing "in 1991 that amount was considerably lower than it had been in 1990" ?

Why do you add (total coal mined in 1991 - total coal consumed in 1991) to total 1990 coal?
- I mean, shouldn't it be a way of expressing 1991 total coal?

I don't have any problem simplifying the formula leading to the correct answer.

I just cannot figure out how you came up with "Total 1990 ... > total 1991 coal"

I would appreciate if you could explain that

Thank you !

[KelseyWoods]

Hi reop6780!

The trick to understanding this question is to realize that the amount of coal tallied at the end of 1990 carries over into 1991. This means that the amount of coal that Country Q had at the end of 1990 is also the amount they had at the start of 1991. That means that if they have less coal at the end of 1991 than they had at the end of 1990/beginning of 1991, then they must have consumed more coal than they mined over the course of the year.

I actually explained this question in another post on this forum a few months back so I'm going to link you to that explanation as well.

Hope this helps!

Best,
Kelsey

[yrivers]

Hi,

Thank you for all the explanations above. Everything makes sense. I have one specific question: how are we guaranteed that the coal went negative into last year's reserves?

For instance, we could argue that:

1991 coal supply was 30 tons
1990 coal supply was 50 tons

How do we know for sure that it was NEGATIVE for 1991? (The bank savings account makes sense above, just don't understand this piece.)

Thanks!
Yaesul

[Robert Carroll]

Yaesul,

Because the running count is lower, there must have been more consumed than mined in 1991. This must be true in order for the total to go lower. It's simply a matter of definition - if the total is lower, then consumption (subtraction) must have been larger than mining (addition) that year.

Robert Carroll

[Adam Tyson]

To add on to Robert's explanation, Yaesul, think of it this way using your numbers:

1990 - 50 tons leftover
1991 30 tons leftover

If in 1991 they mined a billion tons, then they used all billion PLUS 20 tons of the leftovers. Otherwise, there would be at least as much leftover in 1991 as there had been in 1990.

If they mined 1 ton, they must have used that ton PLUS 20 tons of the leftover. Again, they only way the leftovers could have gone down is if they used more than they mined, no matter how much that amount was.

Here's the thing - the 50 tons left over at the end of 1990 is STILL IN THE TALLY in 1991, right? It doesn't disappear. It's still coal that was mined and not consumed. The only way the tally goes down from 50 to 30 is if you use some of the leftovers from a prior year. This is the point that a lot of students fail to account for when they first encounter this question. I hope this helps clear it up!

[adlindsey]

Now I'm supposed to assume there's a "roll over" tally that isn't even mentioned in the stimulus of a MBT? Every time I assume things like that, I'm told I'm wrong and that no such assumption exists. Im getting tired of these *** weasels from Newton pulling *** like this. These *** are cheating me and everyone who studies their *** off at this rigged exam. This month made three years since I started studying and I haven't seen any improvements! I've been at a plateau from the start! It seems like you guys just find ways to justify this ***! A and D are also right!

[Jon Denning]

Hey adlindsey - thanks for the comment. First off, you'll note that I edited it to remove any unsavory language. Keep it PG please

Second, let's take a somewhat novel approach to this, and attempt something that I think will help you (and anyone else who reads this) better avoid the trap answers that at first glance can seem so tempting.

You tell me why you think (A) and (D) are wrong.

I know in your post you're saying they're right. But they aren't. And there's ALWAYS an identifiable reason when that's the case.

Look at them again with fresh eyes and a few deep breaths and explain to me why, if you had to do this question over, you feel you would eliminate them. (And don't say you wouldn't eliminate them; the point of this is that if you know they aren't right you have to learn to recognize why they aren't right, so give me the reason for each)

We'll worry about (B) being right later. Focus on removal and give me good reasons to.

[Dave Killoran]

Now I'm supposed to assume there's a "roll over" tally that isn't even mentioned in the stimulus of a MBT? Every time I assume things like that, I'm told I'm wrong and that no such assumption exists. Im getting tired of these *** weasels from Newton pulling *** like this. These *** are cheating me and everyone who studies their *** off at this rigged exam. This month made three years since I started studying and I haven't seen any improvements! I've been at a plateau from the start! It seems like you guys just find ways to justify this ***! A and D are also right!

Hi Alberto,

Thanks for the message! First, there's a difference between an assumption, what they tell you, and an inference you can draw from what you've read. Take a close look at this again in the manner Jon suggests, and see if you can see the difference.

Second, as you have in the past, you are fighting the LSAT again. As I've mentioned before in our many conversations, you can't do that: http://blog.powerscore.com/lsat/you-can ... h-the-lsat.

Last, we aren't trying to find way to justify this; instead, our job is to explain how the test makers think. If we felt they were wrong, we'd say so, and I have done just that in prior instances when I felt wording was unclear or otherwise problematic. I know you well enough from our many emails that I'll be exceedingly blunt here: the test is hard exactly because of these nuances, but you are focusing your energy in the wrong area by complaining about the test itself and who makes it; focus instead on understanding them and their mindset. That is the ONLY way forward!

Now, let's reverse this like Jon suggests, but I also want to expand it: please write a full explanation of what's occurring in the stimulus, as well as what is happening in each answer. We'll then review that and comment. Good luck!

[adlindsey]

I apologize for the unsavory language. It's not directed towards any of the PowerScore staff.

I guess A & D are wrong because they don't incorporate this mythical roll over. Now that I reread this question. I find more problems. I do not know how I am to correctly infer there is a roll over. The sentence with 1991, states, the tally was lower than in 1990. This could mean many different things and not necessarily a roll over. This could mean that in '91, less coal was mined, than in '90, which would be A. Or it could also mean more was consumed in '91, which would be D. The fact that it doesn't explicitly state there's a roll over, leaves it open to many other scenarios.

As far as B, I don't know how this answer is being inferred! And I don't mean to argue with the test, but it isn't making ANY sense! I don't know what "the TOTAL AMOUNT of coal that has been mined throughout the country BUT NOT CONSUMED, means. Does it mean that the country didn't consume any of it's mined coal? If so, that would make B wrong. Or does it mean the left over coal that wasn't consumed, which, I believe I saw on an earlier comment this isn't the case.

I just finished reviewing all the important concepts of each lesson in the course books; and finished redoing all the questions (for the 2nd time) that I got wrong. My biggest weaknesses are MBT, Flaws, and Justify. I have been organizing all the testing material from the course, course books, and PT's I have taken. I wanted to ask if ya'll keep a list of all the PT's that are used in the courses, so I can use those for drilling and know which ones weren't used; so I can use those for actual PT's?