#15 - Any good garden compost may appropriately be used for

[Administrator]

Complete Question Explanation

Must Be True—SN, #%. The correct answer choice is (E)

This stimulus presents a fact set of conditional relationships.

First, the stimulus provides that any good garden compost may appropriately be used for soil drainage and fertility.

GGC = good garden compost
USDF = may be used for soil drainage and fertility

• GGC USDF

Next, the best compost is 40 to 60 percent organic matter and is dark brown in color. We will diagram best compost (BEST) as a subscript of good garden compost (GGC).

• 40-60% organic
  GGCBEST +
  dark brown

However, compost that emits a strong ammonia smell should not be used for drainage and fertility.


SAS = compost that emits a strong ammonia smell

• SAS USDF

Finally, a strong ammonia smell in compost means the organic matter has not sufficiently decomposed.

SD = sufficiently decomposed

• SAS SD

Given that the stimulus is comprised of a fact set, it should not be a surprise to find that this is a Must Be True question. Whenever you have multiple conditional reasoning statements in a Must Be True question, you should be on the lookout for an inference based on a combination of the relationships, and you must always be on the lookout for a contrapositive of one of the relationships to play a role.

Here, an inference is permissible based on the combination of the first and third facts. In the first sentence, we are told that any good compost may appropriately be used for soil drainage and fertility (GGC USDF). The term USDF appears again in the third fact, though stated in the negative (SAS USDF). By considering the contrapositive of the first fact (USDF GGC), we can create this conditional chain:

• SAS USDF GGC

We drop the common term (USDF) to get the additive inference: compost that emits a strong ammonia smell is not good garden compost:

• SAS GGC

Your prephrase is that the correct answer choice will likely test you on the idea that composite that emits a strong ammonia smell is not good garden compost.

Answer choice (A): This choice is incorrect because the stimulus provides no information that relates the percentage of compost that is organic matter to the sufficient decomposition of the organic matter within the compost. As do choices (B) and (C), this answer choice attempts to confuse you regarding the percentages contained in the stimulus.

Answer choice (B): This choice is incorrect because it improperly infers the reverse of the information presented in the stimulus. The fact that the best compost, which contains between 40 and 60 percent organic matter, is appropriate to use for soil drainage and fertility does not necessarily imply that compost with less than 40 percent organic matter will produce the reverse effect.

Answer choice (C): This choice is incorrect because it ignores the separate condition that the compost be dark brown in color.

Answer choice (D): Similarly to choice (C), this answer choice ignores the color of the compost. Also, the facts did not state that the compost must be completely decomposed in order to be good, just that it must be sufficiently decomposed.

Answer choice (E): This is the correct answer choice, because the stimulus told you that compost with a strong ammonia smell should not be used. Therefore, regardless of the color of the compost, the stimulus supports the statement that compost with a strong ammonia smell is not good garden compost.

[Tony_Stark]

I believe the reason I choose D here was that I made the assumption that:

The best garden compost -> (40-60%) & Dark Brown -> Good Garden Compost -> ext...

Why can we not do that here?

Thanks in advance!

[James Finch]

Hi Tony,

The issue with setting up

BGC 40-60%OM and DB GGC

is that you have to realize that BGC is a subset of GGC, and that not all composts that are 40-60% organic matter and dark brown are necessarily good garden composts, so the

40-60%OM and DB GGC

represents a Mistaken Reversal, as the setup in the post above shows. This conditional ends up acting as a red herring, however, as the critical A B C inference needed to answer this question is:

GGC SD&F

and its contrapositive

SD&F GGC

and

SAS SD&F

Combine the contrapositive of the first conditional and the second conditional and we have:

SAS SD&F GGC

or the inference

SAS GGC

Answer choice (E) expresses this, as the color is irrelevant, but the fact that the compost is emitting a strong ammonia smell means that it isn't good garden compost.

Hope this clears things up!

[mahsan]

Hi,

I had it down to C) and E) and ended up choosing C. I understand the explanation behind E) but am still not convinced that it is better than C). The explanation on this post says that C ignores the separate condition that the compost be dark brown in color. But those two conditions (dark brown and 40-60% organic matter) are required for the best compost, and I didn't think that both conditions would need to apply to good compost (which is what C refers to) since only the definition of the best compost was stated in the stimulus and the requirements for good compost could arguably be different than the best compost. Is the distinction between good and best not important here? And if so, how do we know to overlook that since a lot of LR questions come down to specific words and what they mean?

Thanks!

[Zach Marino]

Hi,

I had it down to C) and E) and ended up choosing C. I understand the explanation behind E) but am still not convinced that it is better than C). The explanation on this post says that C ignores the separate condition that the compost be dark brown in color. But those two conditions (dark brown and 40-60% organic matter) are required for the best compost, and I didn't think that both conditions would need to apply to good compost (which is what C refers to) since only the definition of the best compost was stated in the stimulus and the requirements for good compost could arguably be different than the best compost. Is the distinction between good and best not important here? And if so, how do we know to overlook that since a lot of LR questions come down to specific words and what they mean?

Thanks!

Hi, mahsan!

Let's break this down starting with the stimulus.

Good compost Can be used for drainage/fertility

Best compost 40-60% organic
Best compost Dark brown

Smelly compost can be used for drainage/fertility
Smelly compost decomposed

From this we can also make the connection that good compost smelly compost

So, C has two conditions for being good compost:
1. Compost is 50% organic. This tells us nothing, since being within the 40-60% organic range is the necessary condition for being the best compost. Conditionally, it doesn't trigger anything and logically, there's no connection to being good compost here.
2. Organic matter is sufficiently decomposed. This triggers the contrapositive of "Smelly compost decomposed", which tells us that this compost isn't smelly. The only other conditional statement not being smelly relates to is "good compost smelly compost." However, since smelly compost is the necessary condition here, it triggers nothing and thus makes no connection to the compost C describes as being good compost.

C might be good compost or it might not be, but the answer choice tells us nothing useful to determine that.

Remember that all answers are either 100% right or 100% wrong on the LSAT, so a good strategy to use is to try to take down the wrong answer choices logically.

E also has two conditions.
1. dark brown (this is the necessary condition of "Best compost Dark brown," thus it becomes irrelevant. It also relates to the best compost not to good compost. This statement is ultimately there to distract you from the second statement which is the key to this question:
2. it smells. Because we know "good compost smelly compost", we can take the contrapositive here "smelly compost good compost." We now know that E's smelly compost isn't good compost. E is most strongly supported.

I hope this helps
As you suggest, I think the distinction between good compost and the best compost is very important to having a clear understanding of this question.

[mahsan]

Zach,

Thanks so much for the detailed explanation. That was super helpful!

[nowornever]

I struggled with this question when I did the timed test, and also again when I went through and did my untimed review. Either way, I arrived at the wrong answer both times. After following the explanations given above, the question is much simpler to understand. Obviously I don't want to be writing out inferences for every LR question, but this question seems to be of the type where it might be necessary for me in order to arrive at the correct answer. Do you have a simple method of recognizing when it may be necessary to diagram the inferences from the stimulus?

Initially, I didn't think it was necessary for this question since although I found the question to be challenging, I thought I was able to sufficiently organize it in my head without writing anything out. Turns out that was not the case.
Any suggestions on how to quickly and accurately attack this type of question in the future and to know if diagramming it might help me catch a mistake?

So glad I found this forum, and many thanks to the professionals who take the time to reply!

[Adam Tyson]

My short answer is "if there are two or more conditional statements, diagram." Why juggle anything in my head when I can use my scratch paper to keep it clear? Just because you can sometimes do it doesn't mean you should! Once you get used to them, diagrams can be fast and easy, and they make the right (and wrong) answers abundantly clear, so any time spent on the diagram usually pays off by saving you time debating and second-guessing in the answers. Think with your pencil!

[nowornever]

Thanks, Adam. I'll start with that rule of thumb and see how it works for me. Hopefully I won't also need to diagram if there is only one conditional in the stimulus.

[ange.li6778]

Hi Powerscore, can we assume that "best compost" is a subset of "good compost"? The stimulus says nothing about the relationship between the "best" and "good" categories, and that's why I ruled out C (along with the reason that C lacked the brown color element). It looks like Zach's explanation above does not assume that "best compost" is a subset of "good compost" while the Administrator's explanation does. I'd love a clarification, thanks in advance!