LG Game 4 Question 23 Explanation, by LSATHacks
On a rule substitution question, the correct answer must:
- Forbid everything normally forbidden
- Allow everything normally allowed
A lot of people miss this second quality. It’s very useful. It means that if one of the answers contradicts a scenario that would normally be allowed, then that answer is wrong.
Likewise, if an answer makes something happen that didn’t happen under the normal rules, then it is wrong.
A is wrong because normally G and Ibanez can go together. Here’s an example; it’s a scenario I made for question 20. It also disproves D:
This scenario proves B is too restrictive (I made this diagram just for this question):
C is a trickier answer. It’s true according to the rules, but it’s not restrictive enough. It allows F and H to be together elsewhere. This scenario is possible with C:
So we can eliminate four answers by recycling one scenario from question 20, and then making two quick custom scenarios. Not bad!
That leaves us with E, which is CORRECT. I covered why in the setup, but I’ll repeat it here.
- Each city must have two managers. F/H can’t go together.
- The three options for each city are G, I and one of F/H
- So, if you are missing one of G or I, you must have the other in order to fill the two spots.
If you are missing both G and I, you’d end up with F + H, which violates rule 2.
Ok, but why does this substitute for the rule? Because it ensures every city is filled with at least one of G or I. There are then no open spaces for F + H to go together. For example:
As per E, every space has either I or G. Do you see any place to put F and H together? I don’t. So E indirectly replaces the rule.
It’s best to prove the right answer. But, if you were short on time, you could also have merely eliminated the first four answers as I did with scenarios above.
For your explanation about why B is wrong I think you placed H incorrectly. The choice states “If Sydney is visited by Fan, then Tokyo must be visited by Hayley”. You don’t have Hayley (H) in the section for Tokyo. You have them under Manila (M).