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Logical Reasoning Elimination

This is the fifth and final article of a series of articles on LSAT Logical Reasoning. The series contains the following articles:

LSAT Logical Reasoning: An Introduction
Logical Reasoning Questions
Logical Reasoning Arguments
Logical Reasoning Answers
Logical Reasoning Elimination

Logical Reasoning Elimination

Learning the types of wrong answers is so important in Logical Reasoning elimination we created an entirely separate lesson article series devoted to it. For now, know that there are certain types of wrong answers that keep coming up on the test, and if you can identify them, you can easily eliminate them.

Even if your prephrased answer didn’t appear among the answer choices, you can quickly eliminate three or four of the wrong answers just by recognizing them as a classic wrong answer choice. Thinking like a test maker really pays off in this step. Elimination is a valid way to get a high score, even if you’re not entirely sure why the right answer is the right answer. No one cares how you get an answer right, so if all else fails, knowing why four answers are wrong is just as good.

You’ll get plenty of practice throughout the TestSherpa LSAT course using the four-step process in Logical Reasoning. But just to make sure you understand how it all works together, let’s revisit the arguments we paraphrased above as complete LSAT test questions. Try your hand at these questions before reading the rest of the article where we’ll break it down into pieces for analysis.

Remember to practice the TestSherpa process for LSAT logical reasoning:

  1. Read question stem
  2. Read and paraphrase the stimulus
  3. Prephrase your answer
  4. Eliminate wrong answers

First practice question:

1. The recent run of forest fires in the Pacific Northwest has led to a sudden decline in the supply of wood pulp and a corresponding increase in the cost of paper. Similar accidents, such as oil spills and the collapse of mining shafts, have led to higher prices for many related products. Undoubtedly, we will soon witness a rise in the price of envelopes and cardboard boxes as well.

All of the following assumptions are present in the author’s argument EXCEPT:

(A) The price of raw materials helps determine the price of envelopes and cardboard boxes.
(B) The cost of envelopes and cardboard boxes is effected by the cost of paper.
(C) Forest fires cause the demand for paper to increase.
(D) There will not be a decrease in other costs associated with the manufacture of envelopes and cardboard boxes that would offset the rise in paper prices.
(E) An increase in the price of paper usually results in a price increase for products made of paper.

Even though it seems counter-intuitive and you want to jump right in with reading that big argument, you need to remember to read the question stem first. We picked a tough one, an All/EXCEPT variety. Basically, the question is asking us to identify four assumptions, cross them out as the wrong answers. The right answer in this case will look like a wrong answer. Wow. If this were early on in the section, I would skip it. But just for the sake of argument, let’s say we’ve already answered all the easy ones and now we’re ready to tackle this one.

Next, read and paraphrase the stimulus. Here is the paraphrase we used earlier:

Forest fires up, paper price up, the same with other resources, thus envelope and box prices up.

Next, it’s time to prephrase an answer.

Remember that we said it is difficult to prephrase an All/EXCEPT question, since the right answer sounds like a typical wrong answer. Let’s try it anyway, because we’ll still save some time and be better prepared to face the answer choices. With this type of question stem, prephrasing and elimination work hand-in-hand.

Since this is an assumption question, to help you prephrase possible assumptions, think about what red flags go up when you read the argument. You’ll learn more about assumptions in the Logical Reasoning series dedicated to assumptions.

One red flag that comes to mind is, just because the cost of one element in the production of envelopes increases in price, what if there is a decrease in another element of production. That is, sure paper costs more, but what if the machines that make envelopes are faster now.

Also, is there a direct link between wood pulp and envelopes? What about recycled paper or other sources?

These are all red flags that point to possible assumptions:

  1. There aren’t other costs that have decreased in producing envelopes, and,
  2. There is a direct link between wood pulp and envelopes

Now let’s take a look at the answer choices and use our prephrased red flags as a guide for our elimination.

(A) The price of raw materials helps determine the price of envelopes and cardboard boxes.

This looks almost like prephrase number 2. This must be an assumption, so cross it off (remember, the wrong answers look like right answers in an All/EXCEPT question).

(B) The cost of envelopes and cardboard boxes is affected by the cost of paper.

This isn’t exactly like one of our prephrases, but it’s close enough to both of them to cross off. We’ll show you other tests later on to prove that this is in fact an assumption made by the author.

(C) Forest fires cause the demand for paper to increase.

Demand? Where did that come from? This is out of scope–the author never talked about demand. The argument is about supply. A smart TestSherpa student would mark this as the right answer and move on. Once you find the right answer, ignore the rest and keep moving. After all, there can’t be two right answers. Just for practice, let’s look at the other two answers.

(D) There will not be a decrease in other costs associated with the manufacture of envelopes and cardboard boxes that would offset the rise in paper prices.

This sounds just like our first prephrase. Cross it off.

(E) An increase in the price of paper usually results in a price increase for products made of paper.

This is close to our prephrases. Later we’ll show you the easy test to perform on any answer to prove it is an assumption. But for now we can be happy we identified (C) as the right answer.

Let’s try another logical reasoning example:

2. Although music downloads have increased steadily over the past 3 years, we can expect a reversal of this trend in the very near future. Historically, more than 75 percent of music downloads have been purchased by people from 18 to 25 years of age, and the number of people in this age group is expected to decline steadily over the next 10 years.

Which one of the following, if true, would most seriously weaken the argument?

(A) Most people 25 years old or older have never downloaded music.
(B) Video downloads have declined over the past 3 years.
(C) New technology will undoubtedly make entirely new entertainment options available over the next 10 years.
(D) The number of different types of music available for download is unlikely to decrease in the near future.
(E) Most of the people who have downloaded music over the past 3 years are over the age of 25.

The first step in the TestSherpa process for LSAT logical reasoning is to read the question stem. This is a weaken question, which asks you to consider additional evidence that would weaken the argument. The best way to weaken an argument — and the way that the LSAT will most likely ask you — is to attack the central assumption. So, basically, this type of question is asking us to find a weakness in the argument surrounding a central assumption.

Next, we read the argument, make our paraphrase, and as we’re reading we’re looking for potential weaknesses that the right answer might attack. As we saw earlier, a possible paraphrase for this logical reasoning argument:

Most downloads 18-25 + fewer 18-25’s in 10 years= fewer downloads in the near future.

Next we prephrase a potential answer choice without looking at the real LSAT answers. The question is asking you to weaken the argument, so we want to attack some of the red flags we might have identified. As we read the argument, we can see a couple of logical jumps that have to do with timeframes. First, downloads are up over the last three years. Second, “historically” 18-25 year olds are downloading the most. Is three years the same time frame as “historically?” We don’t know, the author doesn’t say, but they must be connected in the author’s thinking. Also, the argument tries to tie “near future” to trends over the next 10 years. 10 years doesn’t sound like “near future” to me, so there is another time-based red flag. I’m going to look for evidence that shows that these time-jumps are not accurate.

Unfortunately, if this were your actual LSAT test, the right answer to match our paraphrase doesn’t jump right out (although it does connect to the time-jump issue). Fortunately, we’re studying logical reasoning elimination, so this questions will force us to eliminate the wrong answer — isn’t that convenient?

Let’s look at the answers in detail and practice our logical reasoning elimination skills.

(A) Most people 25 years old or older have never downloaded music.

The age range that the author says does the most downloading ends at 25, so this answer would actually be consistent with the argument. It would strengthen the argument, not weaken it. Eliminated.

(B) Video downloads have declined over the past 3 years.

This seems to attack the evidence, which is a very rare way for the LSAT to weaken an argument. But a careful reading shows that this answer is talking about “video downloads” and not “music downloads,” so it must be out of scope. Video downloads have nothing to do with the argument, so it can neither weaken nor strengthen the argument. Eliminated.

(C) New technology will undoubtedly make entirely new entertainment options available over the next 10 years.

This one is way out of scope. You might have found it tempting because it discusses a 10-year window, but it is too broad to be about music downloads. Eliminated.

(D) The number of different types of music available for download is unlikely to decrease in the near future.

If anything, this barely weakens the argument. Unfortunately, the author didn’t give us any connections about how much music is available to download, only times and age ranges. So it is out of scope as well. Tempting, but no. Eliminated.

(E) Most of the people who have downloaded music over the past 3 years are over the age of 25.

This is the correct answer. It has to do with the time-jump assumption the author made between “historically” and the last three years. The last three years discuss an increase in downloads but not age. Vice-versa with “historically.” The loop that needs closed (the author’s assumption) is that the increase over the last 3 years is tied to the age group that has “historically” downloaded the most music. This answer attacks that head on, and so it is a great weaken answer choice.

That concludes our lesson series. Here are some summary tips to take away:

  • Always read the question stem first and skip the tough questions before wasting time reading the stimulus.
  • Always make a paraphrase of the stimulus. Your words are a lot easier to remember and work with than the stilted language of the test maker.
  • Always, always, always prephrase your answer. The prephrase normally involves an assumption, so just grab onto the red flag and go.
  • If you’re stuck or your prephrase doesn’t work out, don’t panic. Eliminate down to the right answer.

It’s now time to return to our LSAT Test course to choose your next lesson.

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