This is an explanation of the third logic game from Section II of LSAT Preptest 64, the October 2011 LSAT.
Four bicycle riders – Reynaldo, Seamus, Theresa, and Yuki (R, S, T, Y) will do a two-day study for a cycling magazine. Each of them will test one of four bicycles – F, G, H, and J. The riders will test one bicycle each day, and they will test different bicycles on both days. Every bicycle is tested each day.
This is a grouping game. There are four bicycles, and four riders. The riders test one bicycle per day, for two days. They don’t test the same bicycle both days.
The first thing you should always do is read through the rules and think about how to setup the game. If you’re stuck, the first question usually shows the best way to do it. Here, it’s best to arrange the bicycles vertically.
The first three rules are simple to add. R doesn’t test F, and Y doesn’t test J. You can draw those variables to the left of each bike, with lines through them. That reminds you not to put that rider with that bicycle.
T has to test H, once. You can draw T to the right of H, to remind yourself. Don’t think you won’t forget. You might get lucky, but in general, people who don’t write down rules forget them at some point. At best, you’ll go slower because you’ll have to look away from your diagram to remember the rules.
The last rule is the key to the game. YS go together on one of the bicycles. Y tests it first, then S.
Where can they go? Not J, because Y can never test J. They also can’t test H.
Why? Because if YS go in H, then there’s no room for T to go in H. So YS go in either F or G.
Note that it’s only on the first day that Y can’t test H. Y could test H on the second day; the rule with S only applies to Y’s first day.
That diagram above tells us every rule. If you’re not sure how it works, then reread the rules to see how it’s built. If you know this diagram well, the game is easy.
Keep one main diagram that looks like this, then draw a simpler diagram when you have to make one for an individual question. You can usually leave off details like the T, since you’ll be often be putting T in H based on information the question gives you.
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