Time Tactics: Simple Global Must Be True Questions

Before I decided I needed time tactics, I often spent two minutes on a logic game question that I should have gotten right in ten or fifteen seconds. The question would be something simple: “Which of the following must be true?” Time after time, I would slog my way through answer choice A, B, C, and D, proving that each one might be false. Then I would reach answer choice E and realize that it must be true–I already had it penciled in on my diagram. The geniuses who write the LSAT know all about people like me, and they routinely set us up for failure. But once you study time tactics, you can beat them at their own game.

A question like “which of the following must be true” is a global “must be true” question. In subsequent chapters, we will talk about “local” questions (where the question begins with an “if” that established a new condition for just that one question) and “must be false” questions. As we explore the different variations of “must be” questions, we will discover the optimal path through all such problems. For now, our “must be method” is very simple:

Must Be Method:
1) Could be easy!

Let’s try this out on the following simple sequencing game. Here are the scenario and rules:

Six law students–Allison, Briyant, Clarence, Daniel, Elisheva, and Faith–decide to chase Pokémon instead of studying. Each student catches exactly one Pokémon at a time. The order in which they catch them is determined by the following rules:

Elisheva catches hers before Daniel,
Allison gets hers first or last.
Neither Elisheva nor Faith catches the first one.
Clarence catches his before Allison or Briyant but not both.

Here is my sketch for this game. The blue items on the diagram are spelled out in the initial rules; the orange items are deductions I have made.

Note: several of our time tactics depend on being able to quickly and accurately check through all the rules, so I list all of the rules in order. If a rule can be completely expressed directly on the diagram, I note that to the left of the rule number; otherwise I write in the rule to the right of the rule number.

Turn on your stopwatch app and see how long it takes you to answer the following question.

Which of the following must be true?

A) At least two students catch a Pokémon before Allison.
B) At least two students catch a Pokémon before Briyant.
C) At least two students catch a Pokémon before Clarence.
D) At least two students catch a Pokémon before Daniel.
E) At least two students catch a Pokémon before Elisheva.

How long did that take? Think about the way you went about answering the question.

Now let’s apply our “could be easy” tactic to this same question. Every single answer mentions “at least two students,” which ought to focus our attention somewhere on the diagram. If at least two students must go before somebody, that somebody can’t go first or second. A quick look at the diagram shows that Daniel is the only student who can’t go second–and he can’t go first, either. Answer choice D is about Daniel–and we’re done!

Your elapsed time for this question, which includes reading the question, looking at the answers, checking the second spot on the diagram, and finding answer choice D should be about fifteen to twenty seconds.

Note–this kind of speed depends on having deduced that Daniel couldn’t catch the second Pokémon when you first set up the game. If you don’t routinely see such deductions when you first go through the rules, you need more work on logic game basics. Don’t worry about that now, however–throughout this book, you’ll have my diagrams in front of you as you tackle each question.

Let’s sum up what we’ve learned about the “could be easy” rule. A “must be true” question could be so easy that you can just look at your diagram and find the answer in a matter of seconds. This is especially likely to be true if you made some good deductions on your setup. When you see a global “must be true” question, quickly skim through all five answers to find out whether you have already figured out the answer. If you have, grab that answer and go–you don’t need to look any further!

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