This is an explanation of the third logic game from Section III of LSAT preptest 37, the June 2002 LSAT.
Three shelves of a bookshelf (1, 2, 3) has six books on them. The first shelf has one book, the second shelf has two, and the third has three books. The books consist of two grammar books- one in Farsi and one in Hausa (F, H); two monographs – about phonology, and semantics (P, S); and the remaining two books are novels – one written by Vonnegut, and the other by Woolf (V, W)
This is a grouping game. It’s also one of my favorite games, because it lets you figure out almost everything before you start. I love those games.
[Note: The LSAT has changed since I first wrote this. Games like this are now rare, and up front deductions are less common. But the skills involved in making this up front deduction still directly apply to the questions newer games ask. Most questions on newer games will give you a single new rule that allows you to make a series of deductions like this.]
But it isn’t always obvious how to do that, so I’ll show you how to approach this sort of game.
First, the basic diagram looks like this:
If you’re unsure how to set up a game, take a look at the first question. Notice they’ve set it up the same way I have.
Next, you should draw the variables. This is important whenever variables are split into groups.
Once you’ve finished your setup, you should look back at this diagram and remember which variable is a novel, a monograph, etc. On logic games, it’s very important to load that type of information into your short term memory.
The game can be split into three scenarios
Now, I said something about splitting the game into three scenarios. You can do that with the second and third rules (I’m going to ignore the first rule for a moment.)
The monographs, P and S, can’t go with each other (rule 2). And they can’t go with V, either! (rule 3)
V, P and S must all be kept separate. So there is one for each group.
For instance, one of P/S could go in 1, the second could go in 2, and V could go in 3. It looks like this:
You may find it tough to see this type of deduction during a game. The trick is to look for rules that mention the same variable. Rules 2 and 3 both mention monographs.
There are only two other ways of arranging that, shown below.
I’ll call them scenarios 1, 2 and 3, in order. (I’m numbering the scenarios based on where Vonnegut appears)
V, S and P must always be keep separate. Always. This is the cardinal rule of this game. If you remember it, the game is easy. If you forget it, the game is hard.
Now we can look at the first rule. You must always put at least one of the novels (V or W) on the same shelf as F. So F needs two spots: one for F and one for the novel.
Remember these two things:
- V, P and S are separate
- F always goes with V or W
Did you memorize the two things from the previous page? Seriously, that’s all you need to follow along and do this game. V, P and S are separate. F always goes with V or W.
In the first scenario, V is already in group 1. So W has to be the novel that accompanies F. Only group two has the two spaces to fit them in. That leaves H to go in group 2.
In the second scenario (when V is in 2) we have more options. F could go in 2 with V, or F could go in group 3 with W. The only thing we can’t do is put W in 2. Then both V and W would be together and there would be no novel left to go with F.
So W has to go in 3, and then F and H are split between the other two groups.
In the third scenario (when V is in 3), there’s only space for F to go in group 3. V is already in group 3, so the novel requirement is satisfied. That leaves H and W go fill the other spots in groups 3 and 2.
F can’t go in group 2 because there would be no novel there.
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