LSAT Logic Games is the core of the LSAT Test. This video shows you LSAT Logic Games Tips.
LSAT Logic Games Tips [Video Transcript]
Hi, welcome back to CaseBriefs LSAT course. My name is Sean Murphy. Today we’re going to have an introduction to logic games. Logic games are, for a lot of students, the scariest section of the LSAT. We’ve all had to do reading comp before on the SAT, or some other standardized tests, and commons sense is enough to get us, at least started in the logical reasoning section but very few of us have ever had to put Herald, Gupta, Ingrid, Gerome, Calleel, and Lucrecia in some kind of order to see in what sequence they’re going to view a rental apartment, or seat seven diplomats around a circular table. The logic games are kind of unique in the world of test prep. There’s nothing quite like them, and so they’re very foreign. They’re very strange, and they seem quite alien to the vast majority of LSAT students. But one thing that I really like about logic games is that, with the vast majority of my students, I see the most dramatic improvement.
A lot of my students start out only being able to get to two games, if that, and they complete their studies able to achieve a perfection or near perfection on all four logic games. With logic games we can learn some tried and true strategies to attack the different kinds of logic games and achieve a great, great deal of improvement. So, this section, really invest your time in it and you’ll see some really, really impressive results.
We break the logic games section into three major game types: basic sequencing, advanced sequencing, and grouping. Basic sequencing, which we’ll cover today, is the most common kind of logic game and you really have to master these games in order to do well on the more difficult games in the other game sections. Every game section that I’ve ever seen has at least one basic sequencing game, and so you’ve got to master these tools before you can move on and tackle the more difficult games. Before we actually look at a specific game let’s take a look at the June 2007 game section and I’ll tell you what category each of these games fits into.
The first game is actually a sort of nebulous fourth category, kind of a wild card game. It’s sort of weird, and it doesn’t really fall nicely into any of those three major categories. We’ll look at it later in class today, but for now I’m just going to explain a little bit as to why it’s kind if strange. You have five digits to put in some sequence, so it looks like a sequencing game, but the rules tell you nothing about what comes before or after. The rules are actually kind if strangely mathematical. “The second digit has a value exactly twice that of the first digit.” That’s the third rule. That’s not typical for a sequencing game.
So let’s move on to the second game, and this also might look like a sequencing game because it has days of the week. Days of the week have a natural order; Thursday is always before Friday, Friday is always before Saturday. So typically when a game has days of the week it’s a sequencing game, but the rules here have nothing to so with the order. It’s all about how these characters are going to group together. If we look at the first rule, “On Thursday Harvest is shown, and no other film is shown after it on that day.” That means that Harvest is the last film in Thursday, but I don’t know who can come before Harvest. I just know that Harvest is last, and then I have a couple other rules that tell us that the other characters are last Friday and Saturday. So it’s not a sequencing game. It’s more of a grouping game. How are these three films, or characters, going to group into three different days of the week?
The third game, however, which we’re going to cover in depth, is a much more typical, basic sequencing game. So let’s take a look at it. “A cruise line is scheduling seven week long voyages for the ship, “Freedom.” Each voyage will occur in exactly one of the first seven weeks of the season, weeks 1-7. Each voyage will be to exactly one of the four destinations Guadalupe, Jamaica, Martinique, or Trinidad. Each destination will be scheduled for at least one of the weeks. The following conditions apply to Freedom’s schedule.”
So I have seven weeks. I have four destinations, and we’ll call those characters that you put in these different weeks or slots the “characters,” and if I look at the rules, there are rules about who comes before, who comes after, who has to be immediately next to one another, so this is what we call a basic sequencing game.
Now, there’s a couple things that are a little strange about this game even if I’m going to put it in the basic sequencing category. There’s four characters and seven slots. We’ll look at a game later today which has a one-to-one corespondents. Meaning, that there’s the exact same number of characters as there are slots to put them in. So this game is a little strange but I wanted to cover it first because it’s from the test that you just took, and I’m sure a lot of you have questions about it. Before we get into the particulars of this game I want to talk a little bit about your game set up and this applies to every logic game.
So they have these squiggly lines here are that first introductory paragraph. Then you’ve got some rules, and then you’ve got the questions. Every logic game has at least five questions. Some will have six or seven. There’s always 22 to 23 logic games questions per section. So actually it’s the section with the least number of questions that makes some of you feel a little better but it’s still a section that you should look at very seriously and I’m sure you’ll see a dramatic improvement.
Now, we want our set ups to be as consistent as possible. We want our set ups to look the same from game to game to game. So what I like to do is to put my characters along the left hand side, so that would be Guadalupe, Jamaica, Martinique, and Trinidad always along the left hand side of the page. The basic set up, the seven weeks or slots, somewhere around here below the second column of questions, and then leave space for the rules between the characters and the set up.
You only have this page to work on. You only have the page of the game itself to do all of your set up, and all of your deductions. You get no scratch paper on the LSAT except for the un-scored writing sample part of the LSAT. So you need to be as efficient as possible with the page you’re given. You don’t want to do any work on other pages in the logic game section because that will ruin those pages for those games. And you’re not allowed to turn to other sections of the test, so you need to be as precise and as concise as possible on the page where you do your set up and your deductions.
Now let’s take a look at how to do this set up. So as I said characters, along the left hand side of the page. Characters are G, J, M, and T. Guadalupe, Jamaica, Martinique, and Trinidad. Now we write our one through seven. Now it’s time to diagram the rules. First rule: “Jamaica will not be it’s destination in week four.” Well, that’s the kind of rule we can write right into the set up; no Jamaica in week four. I suppose we could also do this but that’s kind of redundant. We’ve already got it in the set up so let’s get rid of that. We want to save as much space as possible.
Second rule: “Trinidad will be it’s destination in week seven.” So we can write a positive T right there telling us that Trinidad will always be seventh. These first two rules are gift rules. They just tell us something that’s always true about the game. We like them, we thank the LSAT gods when they give them to us because they’re easy. Now the rules get a little more difficult.
Rule three: “Freedom,” that’s the name of the ship not a character or destination, “will make exactly two voyages to Martinique and at least one voyage to Guadalupe will occur in some week between those two voyages.” Well, we could diagram that M, and to display a relationship that’s not precise just characters that are before or after one another just use a dash. M-G-M. There’s going to be G between the two M’s. Also, it tells us there’s exactly two Martiniques, because, as we know, four characters, seven slots to put them in. Some characters are going to go more than once. Now this isn’t the only G. There could be other G’s outside of the two Martiniques, so we have to remember that, as well.
This next rule is really interesting. “Guadalupe will be it’s destination in the week preceding any voyage it makes to Jamaica.” That word “any” is really important. As we discussed in the previous lesson “any” introduces a sufficient condition. So we can rephrase this rule. Any time we go to Jamaica there has to be a Guadalupe immediately before that Jamaica. So, that’s how we would diagram this rule. Jamaica requires a Guadalupe before the Jamaica.
There’s a couple of incorrect ways to diagram this rule. Now, before I move on, when there’s a precise relationship, characters immediately before or after one another, or it’s simply adjacent to, or sometimes characters that can’t be next to one another, we put that in a block. So it’s the dash for characters simply before or after, a block for characters immediately next to. Now, if we just diagram this rule with a G-J block, well that’s partially true. Every character is going to go at least once so there’s going to be a G-J block in this game, but that doesn’t capture the full meaning of the rule because every time there’s a Jamaica, there needs to be a Guadalupe before it. So there isn’t just one G-J block. There could be, but there could be more than one of Jamaica goes more than once.
Another thing, too, is that Jamaica needs Guadalupe. Jamaica’s the sufficient condition here. Guadalupe could go on it’s own. Guadalupe doesn’t need Jamaica. Jamaica is the needy character here. It’s the character that brings another character along with it. So that’s an important thing to note that Jamaica’s kind of a troublesome character in this game. Jamaica’s going to result in another character being immediately before it. So Jamaica will be involved probably in a lot of hypothetical situations that can’t be true because it’s difficult to put Jamaica in certain slots. I mean already we know it can never be in four, but also we know that Jamaica will always bring a Guadalupe before it. So having multiple rules about a character, good indication that that character is going to be really important when solving the questions. Now the last rule, “No destination will be scheduled four consecutive weeks.”
We could, I suppose do a not G-G, a not J-J. Of course that would be impossible anyway because of the Jamaica-Guadalupe rule, but there’s really no need to write out four anti-blocks like this. This is the kind of rule which is so fundamental to the game that you probably need just to remember it. I don’t think that you need to spend the time to write out these four anti-blocks. So what I would do, I would write a little R next to this rule just that you’re going to remember it that you can never have consecutive characters.
Let’s talk about deductions, now. This game, as a basic sequencing game, does not have a whole lot of deductions. We know that Jamaica can’t be fourth. We know that Jamaica needs a Guadalupe before it. So we know that Jamaica can never be first. That’s something we can say, but that’s really about it. We might be tempted to think that Guadalupe can’t be first, or maybe it can’t be sixth because it has to have a Martinique after it, but that’s not really the case because there can be multiple Guadalupes in this game. So we really can’t do a whole lot of deductions in this game.
We’ll see games later today where there are some more deductions we can do, but generally, with basic sequencing games where you have one set of characters and only one row to put them in, not a whole lot of deductions. Don’t feel that you have to do a whole lot of deductions before moving on to the questions. Some games lend themselves to more deductions and most games, there’s not a whole lot you do. You only get points for getting the questions right. So, if you spend so much time worrying about deductions that you don’t have enough time for the questions, you’re really shooting yourself in the foot. So, if you understand the differences between the game categories, you’ll be a lot better off to decide, “Okay, this is a game where I should be doing more deductions,” as opposed to game like this where you don’t need to do that many.
All right, now let’s look at these individual questions. The first question: “Which one of the following is an acceptable schedule of destinations for Freedom in order from week one to week seven?” Most sequencing games start out with a question like this called a list question where each of the answer choices lists all of the different characters in the order they supposedly appear in. Now, these questions are kind of a gift, too, because you don’t have to do a lot of writing on your own. You can just knock out wrong answers based on when they violate the rules. They’re also a good opportunity to test your understanding of the rules, to make sure you’ve diagrammed the rules correctly and even if answer choice A looks perfect to me, I always test out B, C, D, and E because if I made a mistake in diagramming the rules or in my understanding of the game, I want to catch it early on. I don’t want to get to number 17, the last question in this game, and then realize that “Oh, there’s two right answers or there’s no right answer. I must have done something wrong. Maybe my whole game is compromised.” It’s much better to catch a mistake early on in the game. So take a little bit more time than you might think is necessary for some of the easier questions and then move on to some of the more difficult questions.
So, let’s take a look at these answer choices. Answer choice A: “Guadalupe, Jamaica, Martinique, Trinidad, Guadalupe, Martinique, and Trinidad.” Well, we have Trinidad last. We have a Jamaica second, preceded by a Guadalupe, we’ve got two Martiniques, and a Guadalupe between the two. So this actually looks really good. Let’s go on to the other answer choices. We’re going to hold on to A.
Answer choice B: There’s two Martiniques but only a Trinidad between them. So we can get rid of answer choice B. Answer choice C: Jamaica is first. There always needs to be a Guadalupe before Jamaica so we can get rid of answer choice C. Answer choice D: Jamaica is fourth. We know we can’t have that, so D is out. And answer choice E: I have Trinidad second and fourth but not last. So that means that E is wrong. We’re left with A the correct answer. But even though A looked perfect I still wanted to test out B, C, D, and E.
Now, some people like to do these list questions a little differently. Some people like to take a rule and go down all five answer choices. So they’ll take the “Jamaica can’t be fourth” rule and just look at all of them, D is the only one that violates it. They’ll eliminate D and then go to the next rule and so on and so fourth. Either way I think it’s actually fine. My way works for me. I would suggest testing out both ways but either way make sure you understand not only why the right answer is right but why all the wrong answers are wrong.
Now, let’s take a look at number twelve. “Which one of the following cannot be true about Freedom’s schedule of voyages?” This is an early question in the game, obviously, it’s the second question. And it’s asking us what cannot be true. So it’s the kind of question that we often can figure out before even getting to the question. It’s the kind of question that should reflect our understanding of the game without doing too much work. Answer choice A: “Freedom makes a voyage to Trinidad in week six.” Well, if we’ve written the Trinidad in week seven, we can see right away that Trinidad can’t be week six. We know that the different destinations, the different characters, can’t be consecutive.
If number 12 were really hard, if we had a tough time with it, we probably did something wrong. We may have misunderstood a rule or maybe our understanding of the game is off. The earlier questions in the game, the questions in the first column, tend to be a lot easier than the later questions. So, if we really had trouble with 12 we might want to reconsider the work we did and make sure that our rules, or our diagram of the rules, reflect the actual rules.
Number 13 is our first question that starts with an “if.” So it’s actually giving us a condition, and then we have to decide in this case which of the following could be true. So what we’re going to do, we’re going to write out a number 13, and if possible write out your hypotheticals next to the question. Now, if you look at this page there’s not a lot of room next to the question but try to do as much work as you can next to the questions that the hypotheticals refer to because that way if you do all your work at the bottom of the page that bottom of the page is going to fill up really quickly. So try to do your work sometimes at the top of the page, like for number 14 or next to a question, if possible. But we’re going to start out putting the character that they tell us to put and where they put it, and then we’re going to see if any deductions follow from that.
Here’s our one through seven. It gives us two Trinidads, the one that’s always in week seven and one in week five. Which of the following could be true? A: “Freedom makes a voyage to Trinidad in week one.” Well, there’s nothing in the rules that tells us that we can’t visit a certain destination three times, so let’s see if we can have Trinidad in week one. Well, that leaves a question. Where do we put our Jamaica? As I said earlier, Jamaica can’t go fourth, can’t go first, needs a Guadalupe, so it can’t go sixth. It can never go fourth, and if I put it at week three, I only have two slots left for the two Martiniques but there’s no Guadalupe between them. So answer choice A is out.
Now let’s look at answer choice B. “Freedom makes a voyage to Martinique in week two.” Well, we’re going to have the same problem, Where to put Jamaica? Jamaica can never be fourth, it can’t be sixth here, it can’t be third because it needs a Guadalupe before it, and it can never be first so answer choice B is out.
Answer choice C: “Freedom makes a voyage to Guadalupe in week three.” Again, we have the Jamaica problem. It can never be fourth. It would be nice if it could be fourth because there’s a Guadalupe right there. It can’t be sixth here, it can’t be second because that would put only these two slots for my Martiniques and there’s no G between the two M’s, so C is out.
Answer choice D: “Freedom makes a voyage to Martinique in week four.” Alright, well I think by this point we’re so sick of… well, actually we kind of like the fact that Jamaica’s gotten rid of all these wrong answers but we’ve realized that where to put Jamaica is kind of the key to this game, and we figure that out initially because it was involved in so many different rules. If we put Martinique week four I’m definitely going to want to put Jamaica third. That’s going to put a G before it. I can them put my M to surround the G. And then I’ve got this open space here which I can put a G or an M. It doesn’t really matter because this works. This fulfills the Jamaica problem and I’ve got a valid hypothetical here. So just for argument’s sake let’s put G there. I’ve got two G’s, Two M’s, Two T’s, and one J. This works. I’m going to choose answer choice D and move on.
Let’s take a look at number 14. “If Freedom makes a voyage to Guadalupe in week one and a voyage to Jamaica in week five, which one of the following must be true?” So it’s another question that starts with an “if.” So we have a specific condition that we need to write in a hypothetical, but this unlike 13 is a must-be-true question. So we probably can do more deductions before moving on to the answer choices, so let’s write this out.
So if Freedom goes to Guadalupe in week one, and goes to Jamaica in week five, now we know that Jamaica going in five is going to force a Guadalupe in four. Don’t forget to write your Trinidad in seven because it’s always in seven. And now let’s look at what’s going on here. I’ve got two Guadalupes in one and four. I need to have my Guadalupes, at least one of my Guadalupes, surrounded by two Martiniques. I could put one of the Martiniques in two or three but I definitely need one in six. The two Martiniques have to surround the Guadalupe, so one of them has to go there. That’s a big deduction for this question. That wasn’t given to me in the question itself. Let’s take a look at our answer choices and see if Martinique going sixth is one of the answer choices.
Well, A says Jamaica’s in week two. No that’s not the case here. That could be true but it doesn’t have to be. Trinidad week two, looks like it could be true but it doesn’t have to be. Martinique week three, definitely could be true, but I’m looking for Martinique week six because we definitely made that deduction. D, Freedom goes to Guadalupe in week six. We know that can’t be true. E, Freedom goes to Martinique in week six, that’s exactly what we found. With an “if” question that’s a must-be-true. We can probably figure out the answer before going on to the answer choices, and that’s the way to do it.
Now this next question, “If Freedom makes a voyage to Guadalupe in week one and to Trinidad in week two, which of the following must be true?” We can actually use our previous hypothetical, and that’s definitely what we should be doing as we move on to the later questions in the game. In the earlier questions 11, 12, 13, it’s all about getting used to the rules, learning the rules of the game, and applying them to the questions maybe taking a little bit more time than we think is necessary.
As we get to the second column we want to get the heck out of this game and move on to the next one. So if we can use the work that we’ve done already, then that’ll really help us move more quickly through the later questions. So let’s see if we can eliminate some of these wrong answers based on this previous hypothetical.
So Guadalupe did go in the previous question week one. What we’re going to do is because we left two and three open we’re going to put a Trinidad in week two, and we know this works if we put a Martinique in week three. Now I don’t know if this has to be the way it works out. All I know is that this is a possibility with Guadalupe one and Trinidad two as we’re told to do in question 15.
So I look at answer choice A: “Freedom makes a voyage to Martinique in week three.” Hey, it happened here, but I don’t know if it had to happen. So I’m just going to hold on to A. I can’t pick it. If this was a could-be-true question, I could choose A and be done with it but it’s a must-be-true. I can use previous work to eliminate wrong answers on must-be-true questions. I can use previous work to choose correct answers on could-be-true questions but not the other was around. Just because Martinique happened to go week three here I don’t know yet if it had to go in week three.
But I can definitely say that Martinique doesn’t have to be four because I have a G there. So I can eliminate answer choice B. I can definitely say that Martinique didn’t have to go five because I have a J there, so I can eliminate answer choice C. I can definitely say that Guadalupe didn’t have to go week three. So I can eliminate answer choice D. And I can definitely say Guadalupe did not have to go week five, so I can eliminate answer choice E. I’m left with A, and without doing much work at all I got the correct answer by using work from a previous question and that’s exactly the way you should do it on a logic game. Let the work you’ve done work for you. If you keep writing out new hypothetical after hypothetical, you might spend a lot more time on a game than you need to.
Okay we’re almost done, and this is going pretty well, so let’s take a look at these last two questions. Number 16: “If Freedom makes a voyage to Martinique in week three, which one of the following could be an accurate list of Freedom’s destinations in week four and five?” Well, I have Martinique week three but I don’t have any answer choice that has a G and a J. That would have been great, but probably a little bit too good and they’re never that nice to us on the LSAT. So let’s take a look at a new hypothetical for question 16.
So Martinique’s week three, and we’re looking at weeks four and five. Well I don’t see any reason why Guadalupe and Trinidad can’t go weeks four and five. I’m looking at answer choice A, so let’s try it out. Well, that definitely means I have to have my Trinidad in week seven as always. And I can put my other Martinique week six, so I can take care of the Guadalupe-Martinique rule, and then I have spaces one and two free for Jamaica and Guadalupe. It works. Answer choice A works. It’s a could-be-true question, so I have no reason to test out the remaining answer choices.
As I said we’re approaching this game as if we’re in a real game section. If you’re on a could-be-true question and you’re at the second to last question of the game and it works, you take that and you move on to the last question.
The last question is a global must-be-true. Which of the following must be true about Freedom’s schedule of voyages? We can definitely use our previous work here to eliminate wrong answers, and we can also use what we’ve learned about the entire game to get to the right answer. So, 17, “Which of the following must be true about Freedom’s schedule of voyages?” A: “Freedom makes a voyage to Guadalupe either in week one or week two.” Well Guadalupe’s two here, one here, and one here. That definitely looks like it’s a contender. I can either test that or move on and see if there’s an answer choice that looks like something we definitely know is true.
Just for the sake of argument I’m going to test it. Can I make Guadalupe somewhere other than week one and two? I’ll do the work up here. Can I make Guadalupe week three? Or, better yet, let’s try to make Guadalupe week five. So I can put my Jamaica, sixth. My Trinidad is seventh. I can put my M-G-M two, three, four, and I can put a Trinidad first. So answer choice A doesn’t have to be true, so I can eliminate it.
Let’s take a look at answer choice B. “Freedom makes a voyage to Martinique either in week two or week three.” Well, I can look at number 13 and see that definitely doesn’t have to be true because there’s no Martinique in week two or three. So I can get rid of answer choice B. C: “Freedom makes at most two voyages to Guadalupe.” I don’t really want to test that out; it looks like you can go a third time. It’s not as restricted as some of these other characters. And also if I look ahead C, D, and E are very similar. C: “Freedom makes at most two voyages to Guadalupe.” D: “Freedom makes at most two voyages to Jamaica.” E: “Freedom makes at most two voyages to Trinidad.”
Well, they’re all very similar but hopefully by now you can see that I’m most interested in answer choice D, Freedom makes at most two voyages to Jamaica. Why? Because I know that Jamaica has been such a problematic character. Going back to the beginning Jamaica always needs a Guadalupe before it. Jamaica can’t go fourth and first, and if I put in three Jamaicas, more than two, I’d have to have three Guadalupes. That would be six characters. Put my Trinidad in there, there’s not room for even one Martinique let alone the two that we’re required to have.
So answer choice D is correct. And if you’re really good, you look at all the answer choices and think, “Which of these is most likely to be true?” An answer choice that limits Jamaica is definitely the answer choice most likely to be true. Of course, you don’t want to choose it on a hunch. You want to figure out why it’s really correct, but if you’re really good at logic games you’ll be able to predict based on your knowledge of the characters which one is most likely to be in which kind of correct answer. It’s a must-be-true question. So we’re probably looking for a character that’s highly restricted, and in this game that’s Jamaica. So number 17 answer choice is D and we’re done with this game.