Deductions in analytical reasoning | Introduction

An introduction to deductions on the Analytical Reasoning section

Making deductions is arguably the most important skill on the LSAT (as well as in your legal career), and the Analytical Reasoning section is no exception.

The more deductions you're able to make about the scenarios and rules on an AR setup—before you look at the questions— the more quickly and smoothly the questions will go.

Set yourself up for success.

It can be very tempting to scribble down a diagram and rules and then jump to the questions—especially given the test’s time constraints. But if you take the time to make deductions before moving to the questions, you won’t find yourself making the same deductions repeatedly in each question and wasting time.

Know what to look for

Many students feel that they have to get “lucky” in order to find deductions—sometimes they see deductions, but other times they don’t. In this article, we’ll show you what to look for so you’ll have a better sense of when it’s time to stop deducing and move on to the questions.

Get your GEARS moving

Deductions are, at their core, simply a combination of information. But since students can often get intimidated by all of the different ways that the test can present information, we’ve created an acronym to help focus your attention on different kinds of combinations. If you think of GEARS as you hunt for deductions, you can use it as a sort of mental checklist to look for certain common types of deductions.

Groups

Looking at Groups can often yield helpful deductions. As a reminder, a “group” is two or more elements that have some kind of relationship to each other. Groups are great for making deductions because the more an element is restricted, the fewer places that element can go. That means the bigger the group, the more deductions we can make!

In ordering setups:

A...B (A is sometime before B).
AB (A is immediately before B).
A _ _ B (A is exactly three spots before B).
A...BC (A is sometime before B, who is immediately before C).

In grouping setups:

AB (A and B are in the same group).
not AB (A and B are not in the same group).

Deductions:

For ordering setups, each of the above ordering examples yields quick Groups deductions. In the example of A...B, the two deductions we should immediately make are:

1) A cannot be in the last available spot and
2) B cannot be in the first available spot.

A similar, guaranteed deduction doesn’t exist for an AB group in a grouping setup, but here’s one you can make: suppose that there are two groups, a Hawaii group and an Argentina group. One of the setup rules tells us that A and B can’t be in the same group. We can therefore deduce that either A or B must visit Hawaii and the other one must visit Argentina.

Established Elements

Established elements are elements that are definitively placed, for example, “A goes jogging on Monday” in a setup in which 5 people go jogging one at a time from Monday through Friday. We now know everything about A and everything about Monday, and the reason that this is important for making deductions is that one spot has been completely removed from all possibilities. The more that’s established, the fewer possibilities there are for the remaining, unestablished elements.

Top tip: Each time you establish an element definitively, you can essentially start your GEARS checklist all over again. That’s because the game has changed, once you establish an element. Things that were possible before are no longer possible, so it’s important to look at the impact of establishing a player.

Arithmetic

“Arithmetic? I wasn’t told there was math on the LSAT!” Don’t worry—the test isn’t going to ask you to find the equation of a parabola. But sometimes you’ll be able to make certain deductions based on numbers that you’re given. This will happen almost exclusively in grouping and mixed setups.

Suppose we had a setup in which each of 6 employees (ABCDEF) goes to one of 3 movies (Thor, Loki, and Sif). Then we’re given a rule that tells us that exactly three more people see Loki than see Thor. We can make a deduction that either

1) zero people see Thor and three people see Loki, which means that three people see Sif, or
2) one person sees Thor and four people see Loki, which means that one person sees Sif

In other words, our Thor:Loki:Sif moviegoer numbers will be 0:3:3 or 1:4:1, respectively.

This framework is very helpful, as it provides numerical restrictions on what’s possible. For instance, suppose that we’re given a condition that C and D see the same movie; we’d be able to deduce that that movie isn’t Thor, because we already deduced that either zero or one person sees Thor !

Repeats

In all types of setups, look for elements that repeat between two rules or even among more than two rules. Those elements will be instrumental in creating deductions, because you know more about elements appearing in multiple rules than you do about elements appearing in just one rule. Let’s imagine we have a setup in which 5 books (ABCDE) are reviewed on 5 separate days of the month, 1 through 5. Two of our setup rules are:

A is reviewed sometime earlier than B is reviewed.
B is reviewed on an odd-numbered day.

Since B is a Repeated element, we know more about B. For example, we would normally deduce from the second rule that B is reviewed on day 1, 3, or 5. However, since B is repeated in the first rule, we know more when we combine the rules. B can’t be reviewed on day 1, since A is earlier than B. That allows us to shave the possibilities for B down to only day 3 or day 5.

Scenarios

This deduction type is arguably the least obvious but incredibly helpful (when it’s applicable). The basic idea is that if you can break a setup down into only two or three possible scenarios, this allows you to diagram those possibilities and see more of what must be true/false.

Suppose we had a setup in which five students ABCDE perform a musical piece, one after another. One of the rules is that A performs earlier than B, with exactly two performances separating them. Without scenarios, we’d need to note the rule separate from the diagram:

But notice that there are only two ways in which the pair could fit into our diagram! Either A and B are 1st and 4th, or they’re 2nd and 5th. That’s a great opportunity to create two scenarios and understand that every acceptable situation (i.e. every situation that conforms to all of the setup rules) will fall into one or the other scenario:

See how useful the scenarios can be? Let’s say you get to a question that asks you to determine what must be true if C is immediately after B. You would be able to almost instantly determine that only Scenario 1 applies, and that B must be 4th and C must be 5th. That’s part of the beauty of making scenarios.

For more in-depth help in recognizing and making scenarios specifically, you can work through the article How to use multiple scenarios in Analytical Reasoning setups.

We also cover scenarios further with an actual exercise in the article Deductions in Analytical Reasoning | Practice.

Takeaways

Be patient. Developing fluency in deductions takes time (sometimes months!). You should be referring to this article often if you’re having trouble finding deductions on your own.
Repeat the checklist as necessary. Each time you establish an element definitively, start the “checklist” over again—you may uncover new deductions because of that established element.
Don’t rush. If you want accurate deductions, you need to have an accurate understanding of the rules. Take your time in getting the rules right the first time.

What’s next?

Now that you’re familiar with how to look for GEARS deductions, you should go ahead and see if this system works for you as you work through the Analytical Reasoning exercises and explanations in our practice system.

If you’d like more practice with deductions specifically, go ahead and check out our practice article on Deductions in Analytical Reasoning.

These articles also feature setups for which efficiency and success hinge on the initial identification of deductions:

How to approach ordering setups

How to approach grouping setups

How to approach mixed setups

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Sydney Howard
Posted 9 months ago. Direct link to Sydney Howard's post “I get every single questi...”
I get every single question right if I take an additional 25 minutes to complete my AR section, but during the real thing, I struggle. I don't work fast enough and the time stresses me out, what are some good tips to help with test stress for this section and speed?
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llnu70
Posted a year ago. Direct link to llnu70's post “where can i get more prac...”
where can i get more practice questions except practice tests
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jimmeriadee
Posted 4 months ago. Direct link to jimmeriadee's post “So Im confused on the spa...”
So Im confused on the spacing. In the previous problem, it stated A is exactly three spaces away from B, it was shown like this: A - - B. Then in the next example it stated, A is exactly two spots away from B, it was shown like this: A - - B. This is confusing, was there a mistake?
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