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.