Rule substitution questions are harder than other questions, but they’re not as hard as you think. The key is to eliminate silly answers. Remember, four of the answers are wrong. You don’t have to give them any respect. They’re mostly stupid answers. Your goal should be to prove they’re stupid.
An answer can be wrong for two reasons on a rule substitution question:
- It allows something not allowed under the normal rules.
- It restricts something allowed under the normal rules.
I go through each answer and try to disprove it, applying those tests. If an answer seems plausible and doesn’t violate either test, then I keep it as a contender. Once I’ve eliminated some answers, I can test the remaining answers more thoroughly.
A isn’t restrictive enough. It only blocks R from being fourth, and therefore it allows this scenario:
(It’s wrong, because R can’t be fifth normally.)
B seems plausible. Let’s skip it.
C describes something that has to be true (V is always 3rd or 4th), but that’s not what we’re looking for. We want a rule that matches the effects of the original rule, but this new rule allows this possibility:
V is third (like the rule says), but R is fifth, which isn’t allowed.
D isn’t true. In the 1st scenario, Q doesn’t have to be beside R: Q can be fourth. So this answers prevents possibilities that are normally allowed.
E allows possibilities that normally aren’t allowed, like this:
T is shown fifth, so the rule in E is obeyed. But R is no longer 1st or 2nd.
So let’s look at B again. It says that R must be earlier than V. If you look over all four scenarios, you’ll see that V can only be 3rd or 4th.
If V is 3rd, then R must be 1st or 2nd. This obeys the old rule.
If V is fourth, the Q must be 3rd, since Q or V always has to be third (rule 3). So this means that once again R must be 1st or 2nd to be earlier than V.
Therefore, the rule is replaced either way. B is CORRECT.
Livia says
Hi, I really like your explanations thank you so much for your work! But I wondered if you could provide a little more clarity on your reasoning above…question 12 states “which one of the following, if substituted for the constraint that the house in Riverton must be shown either 1st or second…”. I took the if substituted phrasing to signify that the Riverton rule does not apply to the possible answers. So I was confused when your reasoning tested the potential answers against the Riverton rule. Could you provide me with some guidance on where my logic is faulty? Thank you so much!
Nick Major says
In your reasoning for disregarding E, you state that the rule is “If the house in townsend is shown 5th” but the statement is “if the house in townsend is NOT shown 5th”. Because of the rule for the townsend house either being 1st or 5th, then if it isn’t 5th it must be first. If it abides by both the rule that it ISN’t 5th and is either 1st or 5th then it must be 1st. The riverton house is either first or second. Thus, if the Townsend house must be first, then the riverton house is 2nd. I would like to see what is wrong with my reasoning, it would be very helpful.
Tutor Lucas (LSAT Hacks) says
Remember, the rule is saying “IF the house in Townsend is not shown fifth”, and not “the house in Townsend is not shown fifth”. So, the rule allows for the possibility that the house in Townsend IS shown fifth; the rule is saying that in the event that T is not fifth, it will trigger a certain event, but that doesn’t mean that T must not be fifth.
The explanation shows that the rule allows for a possibility that the original scenario does not. If T is fifth (which, again, is allowed by the rule), and there is no restriction on R, then R could be in the fourth position. That’s not something that was allowed in the original scenario. We can, therefore, rule out E. Your reasoning would also suggest that T can never be fifth, and must be first. That would eliminate scenarios that are possible in the original scenario; the original set of rules allows T to be fifth.