This is an explanation of the second logic game from Section II of LSAT Preptest 64, the October 2011 LSAT.
A government needs to assign new ambassadors to Venezuela, Yemen, and Zambia (V, Y, Z). There are five candidates to fill the positions: Jaramillo, Kayne, Landon, Novetzke, and Ong (J, K, L, N, O). You need to use the rules to determine who can be assigned to each country.
This is an in-out grouping game, with three groups. There are five ambassadors, and only three will be chosen.
The first thing you should always do is read through the rules and think about how to setup the game. Some people start drawing right away, but you should think about the best way to set up the game before you draw anything. Taking the time to do things right usually helps you go faster.
If you’re stuck, the first question often shows the best way to do it. On this game, the countries are the groups, and it’s easiest to arrange them vertically.
I’ve drawn the final rule on the left of the diagram. L can only go to Zambia. Another way of saying that is: L can’t go to Venezuela or Yemen.
There are a couple of ways to draw the first rule. This diagram shows that K and N are never together.
But this is incomplete. It doesn’t show that one of K and N has to be in. Also, you can’t connect this type of diagram to other rules.
I’ve come to prefer drawing this type of rule a different way, on games where you can join several rules together (like this one. We’ll get to that soon).
This is confusing at first, but it’s very effective. If you have K, you don’t have N. And if you don’t have N, you do have K.
If you draw the two halves of the rule separately, it’s very easy to forget half of the rule. I get to watch a lot of students do logic games, and forgetting easy rules is one of the most common problems.
So I’ve drawn the two halves together as a reminder. You don’t want to forget that the relationship goes both ways. There’s no logical problem with having the same variable twice on the same diagram. If you are told N if out, you must remember that K is in, and this diagram helps you do that.
Once you split these diagrams into two and write down the full rule, there’s quite a bit you can do. Look at the second rule. We can add it to the first diagram, to get this.
If J is in, you know almost everything. You have J and K, and you’re missing N. You need one of O and L too, to get three ambassadors.
K ➞ N was the other diagram. Here’s the second rule combined with the other diagram:
If you have N, you don’t have K and you don’t have J. And if you don’t have K, you do have N.
You may still be wondering why it’s important to write N twice. Well, some questions may start by saying “K is not assigned to an ambassadorship”. If you don’t write the second N, you might forget about that rule, and only focus on the rule that says J isn’t in.
I can’t count how many times I see students forget rules; the games are designed to make you forget.
When you write both rules on the diagram this way, you literally cannot forget. It’s right there, staring you in the face. You no longer have to think about it, you can simply apply the rules. Most students’ mistakes come from forgetting rules they drew correctly.
Drawing both rules also lets you make a further deduction from this diagram. You need three out of five candidates. If N is in, you lose K and J. So you need O and L to make three.
If N is in, we know almost everything that happens. L is assigned to Z, and N and O go with V or Y.
The last rule is simple. If you see O with V, then K is not with Y.
As it turns out, these diagrams aren’t much use on the questions for this game. But I wanted to show you how to make them, for two reasons:
They usually are very useful.
If you know how to make this sort of diagram, then you truly understand the game. You’ll do well on the questions, whether or not you actually need the diagrams.
You should get in the habit of making deductions and making complete diagrams whenever you can.
There’s one other thing you should know for each game. You should know all of the rules, by heart if possible. If you can’t remember them, then have them all in a list. On this game, you can solve most questions by mechanically applying the rules to eliminate answer choice. The rules are:
1. Exactly one of K or N is in.
2. If J is in, K is in. If K is out, J is out.
3. If O is in assigned to V, K is not assigned to Y.
4. L can only be assigned to Z.
Know these four rules, and the game is simple. A good setup for this game would be the two diagrams I drew below, and the list of rules.
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