This is an explanation of the third logic game from Section IV of LSAT Preptest 72, the June 2014 LSAT.
Five artifacts (V, W, X, Y, Z) originated in Iceland, Norway, or Sweden (I, N, S). The artifacts were recovered from a sunken ship. You must determine the possible country origins of the artifacts.
This is a rules based game. If you know the rules like the back of your hand, this game is easy. If you struggle to remember the rules, this game is hard.
The key to most modern games is to slow down on the setup, and memorize the rules. If you know all the rules, you’ll go much faster through the questions.
There are three groups in this game: Iceland, Norway and Sweden. The first question shows you the best way to set them up:
These are three vertical groups. There are no lines beside them for artifacts, because it’s possible for a country to have no artifacts.
I drew the third rule first. We need more artifacts in Iceland than Norway:
The arrow and the “greater-than” sign are an improvised reminder of this. Note that now we also need at least one artifact in Iceland, so I’ve drawn a line there for that artifact.
I then drew the second rule directly on the diagram. X is from Norway or Sweden. I put this in two scenarios:
In the first scenario, Iceland must have at least two artifacts, due to rule 3.
Note that Norway can have at most two artifacts (in either scenario), in which case Iceland would have three.
Often, drawing dual scenarios leads to extra deductions. In this game, there were no new deductions. However, I do find the dual scenarios are useful for a few reasons:
- They serve as a reminder of the rule about X’s origin.
- They make it easier to visualize possibilities while looking at them.
- They remove one rule from the list of rules.
I find removing one rule from the list of rules significantly simplifies the game. The more rules you have directly on the diagram, the easier it is to remember the remaining rules.
Next, there are two rules that can’t be added to the diagram. WY must be together, and if V is in Iceland, then Z is in Sweden:
If you ever make a mistake with contrapositives, you should also draw the contrapositive of the rule:
However, once you master contrapositives at an intuitive level, you no longer need to draw them.
There’s no major deductions on this setup. So you should memorize the rules before moving on, as the game is going to test you on your mastery of the rules.
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