Tips for the Dreaded “Substitute a Rule” Questions on Logic Games

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If you’ve been playing logic games for long enough, you surely know the feeling: You’re cruising through the game, the questions seemingly answering themselves. A quick check of the rules here, a reference to your scenarios there — it’s all that’s needed to get through the questions. If you’re really feeling yourself, you might mutter something like, “They call me the ‘submarine sandwich,’ because I’m on a freaking roll” (Or … maybe that’s just me). Anyway, you’re feeling great.

But then you get to the last question. Before even reading a word, you can tell it’s way longer than any other question. That is portentous. You think you know what the question is going to ask, but you read the question anyway, hoping that it’ll ask literally anything else. But alas, your fears are confirmed: the last question is the dreaded “substitute a rule” question.

The question asks you to find the answer choice that has the “same effect” in determining the arrangement of your players. A bead of sweat forms on your brow. The pencil that you were just a moment ago holding so confidently droops in your hand like a wilted flower. Panic creeps in, and your well-earned confidence evaporates.

How do you even do these questions again? You’ve heard that you should probably just skip these questions, but you can’t force yourself to do that. You’re a dogged completist. You see things through to the end. The fact that you watched all eight episodes of that not-very-good Idris Elba DJ show on Netflix proves this so. So how can you do these question and (1) get them correct, but (2) not spend an agonizing amount of time on them?

That’s where we can help. These questions can be difficult, but their reputation as one of the hardest questions on the LSAT is at least somewhat overinflated. With a few tricks up your sleeve, you’ll be able to get through these questions without losing your well-earned confidence. So let’s talk about those tricks:

1. The Process

First, the process for doing these questions is fairly straightforward. Check each answer choice, one by one. First, check to see if each answer choice does everything the original rule did. For instance, did the original rule make it so H couldn’t go in the first slot, and had to go before K? Check each answer choice, and determine whether that answer choice makes is H doesn’t go first, but does go before K. If an answer choice allows H to go in the first slot, or if it allows H go after K, that answer choice is wrong. It doesn’t have the same effect on the game. Eliminate it.

Second, check to see which answer choices impose extra constraints on the game — constraints not imposed by the original rule. To have the same effect on your players, the answer choice must impose all of the original constraints, and not any more. So you need to eliminate any answer choice that adds restrictions to the game. For instance, maybe the original version of the rule you’re replacing allowed F, I, L, or M to go into the first slot, but one answer choice says that “either F or M is first.” By preventing I or L from going first, that answer choice imposes extra constraints. So that answer choice is wrong, even if it otherwise restricted the game in the same way the original rule did. Eliminate it.

Only one answer choice will pass both tests. So if you’re following this process correctly, you’ll get to the correct answer. This process is an organized way to get through these questions, so at the very least you won’t feel like you’re guessing. But this process can be laborious and time-consuming. It’s rarely the fastest way to get the right answer, and it’s often not the easiest way to get to the right answer. So use this process as a fall-back plan. If the following two tricks don’t work out, then apply this two-step process.

2. Check for Deductions

Many “substitute a rule” questions are just sly ways to ask you if you made the important deductions in that game. Frequently, you’re tasked with replacing a rule that led to an important inference. The rule you’re replacing interacted with another rule that led to an “a-ha” moment that allowed you to take on me the game with aplomb.

In those cases, the right answer to the “substitute a rule” questions will lead to the exact same deduction or, easier still, will just tell you exactly what that deduction was. For instance, one version of this question asked test takers to replace the rule that “motorbike servicing has to be [performed] earlier than laundry.” There was another rule in that game: “Motorbike servicing has to be either immediately before or immediately after jogging.” So those rules together forced both “motorbike servicing” and “jogging” ahead of “laundry.” The right answer to that substitute a rule question just said, “Jogging has to be earlier than laundry.” Combined with the condition that “[m]otorbike servicing has to be either immediately before or immediately after jogging,” that answer choice would lead to the exact same deduction that you made initially, and would therefore have the same exact effect on the game.

Other times, the right answer will just spell out the deduction for you. Maybe the original rule led to the deduction that a player could only go in the third or fourth slot? The right answer might say exactly that.

So if you know that the rule you’re replacing led to a deduction in you game, it can be helpful and time-saving to scan the answer choices for one that would lead to the same deduction, or one that states what that deduction was. If you find that answer choice and you want to be really sure it’s correct, you can then test it, using the same two-step process that was discussed above. Whether you double-check or not, you’re saving time and mental energy. Instead of having to meticulously test every option, you can quickly and confidently make a selection.

3. Eliminate Any Answer Choice that “Could Be False” in Your Original Set-Up

What about the times when the rule in question didn’t lead to a major deduction, you ask? How can you quickly get to the right answer on those? Well, whether there’s a major deduction or not, there’s a trick that will almost always help you eliminate at least a few incorrect answer choices. That trick? Eliminate any answer choice that “could be false” in your original set-up. In other words, any answer choice that doesn’t have to be true in the original version of the game should be eliminated.

This is due to the idea we just discussed in the “Process” section above — the right answer can’t impose any additional constraints on the game. Essentially, the right answer can’t prevent anything that was possible in the original version of the game. So if an answer choice to the “substitute a rule” question says that J can’t go fourth, check your original set-up. If you look to your original set-up, and you don’t see any restrictions indicating that J can’t go fourth, that answer choice is wrong. Or check your work on previous questions — maybe on a previous “conditional question” (those that say “If so and so is true, then which of the following …”) you see that J was going fourth. That would prove that answer choice is wrong. You can even check the right answer to the elimination question (usually the first question, which asks for an “acceptable” or “complete and accurate” outcome in the game) — if J is going fourth in the right answer to that question, that proves the answer choice in the “substitute a rule” question, which says J can’t go fourth, is wrong.

This method is even easier with scenarios. The right answer will have to be true in all the scenarios you constructed. So if an answer choice could be false in just one of your scenarios, that answer choice is wrong and should be quickly jettisoned.

Usually, this will eliminate at least a few incorrect answer choices. Then, you can simply apply the aforementioned “process” to the remaining answer choices, until you find the option that passes both criteria of that test.

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Armed with the right approach a few tricks, these “substitute a rule” questions don’t have to be a scary time suck. If you “substitute” your current process with these tips, you can “rule” these questions.

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