Atlas LSAT
Logical Reasoning






© 2009 Atlas Prep, LLC
 

All actual LSAT questions printed within this work are used with the permission of Law School Admission Council, Inc., Box 2000, Newtown, PA 18940, the copyright owner.  LSAC does not review or endorse specific test preparation materials or services, and inclusion of licensed LSAT questions within this work does not imply the review or endorsement of LSAC.

Each copyrighted LSAT question that appears in this book is marked with the month and year of the exam from which it was taken, and with the section and question number of the particular question (e.g. December 2006, Section 2, #4).

Table of Contents


CHAPTER 1: Logical Reasoning Overview.......................................................................................................5

CHAPTER 2: Arguments: Read Like a Debater..............................................................................................11

CHAPTER 3: Work from Wrong to Right...........................................................................................................33

CHAPTER 4: Analyze the Structure Questions................................................................................................43

CHAPTER 5: Assumptions.................................................................................................................................71

CHAPTER 6: Identify a Flaw................................................................................................................................93

CHAPTER 7: Conditional Logic for Logical Reasoning..............................................................................113

CHAPTER 8: Inferences....................................................................................................................................125

CHAPTER 9: Strengthen/Weaken...................................................................................................................147

CHAPTER 10: Application.................................................................................................................................177

CHAPTER 11: Explain a Result.......................................................................................................................217

CHAPTER 12: Final Takeaways......................................................................................................................233

 

Logical Reasoning on the LSAT

What is Logical Reasoning?
The Logical Reasoning (LR) section of the LSAT tests your ability to analyze the logical foundations of a given argument. While knowledge of some formal logic principles can be helpful on some Logical Reasoning questions, you certainly don't need prior training in formal logic in order to succeed on the LR section. Rather, your success will be dictated almost entirely by your ability to read effectively and critically. Much of this book will be dedicated to building your reading skills in the context of LR questions.

Here is an example of a typical LR question:

February 1994, Section 4, #18

Advertisement: Attention pond owners! Ninety-eight percent of mosquito larvae in a pond die within minutes after the pond has been treated with BTI. Yet BTI is not toxic to fish, birds, animals, plants, or beneficial insects. So by using BTI regularly to destroy their larvae, you can greatly reduce populations of pesky mosquitos that hatch in your pond, and you can do so without diminishing the population of fish, frogs, or beneficial insects in and around the pond.

Which of the following is an assumption on which the argument depends?

(A)    The most effective way to control the numbers of mosquitos in a given area is to destroy the mosquito larvae in that area.
(B)    Populations of mosquitos are not dependent on a single body of water within an area as a place for their larvae to hatch and develop.
(C)    There are no insect pests besides mosquitos that pond owners might want to eliminate from in and around their ponds.
(D)    The effectiveness of BTI in destroying mosquito larvae in a pond does not require the pond owner's strict adherence to specific application procedures.
(E)    The fish, frogs, and beneficial insects in and around a pond-owner's pond do not depend on mosquito larvae as an important source of food.

The correct answer is (E). We'll be taking a closer look at Assumption questions later on in the book. For now, simply note that this example illustrates the three components that make up every LR question: (1) the argument, (2) the prompt (the question), and (3) the answer choices.


Logical Reasoning on Your Exam
The entire LSAT exam is comprised of the following sections (not necessarily in this order):

 

Note that every LSAT exam will contain two Logical Reasoning sections that will count towards your final score. Thus, just about half of the total questions on the LSAT will be Logical Reasoning questions. To succeed on the LSAT, you MUST be comfortable with Logical Reasoning.

Keep in mind that the Experimental section could end up being a Logical Reasoning section as well. If you do receive three LR sections on your exam, only two of those three sections will actually count towards your final score (unfortunately, it's impossible to know which two as you are taking the exam).

Scoring
Each LR question, and every other question on the LSAT for that matter, is worth exactly 1 point. If you answer a question correctly, you will be credited with 1 point for that question. If you answer the question incorrectly, or if you fail to answer the question, you will be credited with 0 points for that question.

It is important to note that there is no guessing penalty on the LSAT. An incorrect answer is scored the same as a "no answer." Thus, it is to your advantage to answer every single question on the exam, even if some of those answers are wild guesses.

During the scoring of your exam, your points are totaled and then converted to a scaled score between 120 and 180. The conversion depends on the performance of all the other test-takers who took the same exam; a standardized curve is used to assign your scaled score.

From Here to 170+

The Logical Reasoning Dichotomy
When it comes to Logical Reasoning, there is a big difference between the approaches, skills, and attitudes of the average scorer and those of a top scorer:

 

So, how do you move from the left column to the right? First, you must develop a solid understanding of the LR content tested on the exam. This requires a comprehensive look at the various question types that you will face.

Content: Logical Reasoning Question Types
Logical Reasoning questions can be organized into the following categories. Note the relative frequency of each question type:

 

Later on in this book, we will carefully examine each and every question type, and we will introduce the most efficient and effective methods for tackling each question type. It is worth emphasizing, however, that your ability to recognize and understand the characteristics of different question types is only one small part of achieving success on LR questions. While you will use these categorizations to learn the nuts and bolts of LR, the ultimate goal is to see these different question types as mere variations of each other. In other words, the better you get at LR, the less you will focus on the discrete categories represented in the table above and the more you will see each of these question types as a slightly different way to test how well you read.

As we mentioned earlier, your ability to read effectively and critically will drive your success on LR. This is a good time to introduce the important principles that will guide your LR process.

Process: The 3 Principles

1. Read Like a Debater
Research shows that the best readers read with a purpose. We'll examine how to define this purpose by putting yourself in the mindset of a debater.

2. Mind the Details
The difference between a right answer and a wrong answer often comes down to one subtle detail presented in the argument or in the answer choice itself. You MUST mind the details! We'll see plenty of examples throughout the book.

3. Work from Wrong to Right
Wrong answers are much easier to find than right answers. To succeed on the most difficult LR questions, you'll need to change your mindset: your job is NOT to find the right answer, but rather to quickly identify the wrong answers.

Let's get started.

 

Learn more about our Strategy Guides and download free chapter excerpts.

 

 

 

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