Which one of the following, if substituted for the condition that the fourth floor must be examined on either Thursda...

Hope on January 4, 2020

Why not C?

Could you walk through the best approach for rule replacement in general? I though 5 could only be Friday and Saturday so having 4 ahead of it would restrict to Thursday and friday. I thought having it consecutive with 7 would allow for Wednesday and saturday.

1 Reply

Skylar on January 5, 2020

@Tex1610, maybe I can help.

(C) says that floor 4 > floor 5. You are correct that floor 5 is limited only to Friday and Saturday (because 3 > 7 > 5), but this means that floor 4 must either go on Wednesday, Thursday, or sometimes Friday in order to be on a day before floor 5. Note that (C) says "an earlier day," not "one day earlier." The possibility of floor 4 on Wednesday surpasses that of the original rule and is therefore eliminated.

(A) says that floor 4 is either on the same day as or a day consecutive to floor 7. We know that floor 7 is limited to Thursday or Friday (because 3 > 7 > 5). Therefore, if floor 4 were to be examined on the same day as floor 7 in either scenario, it would match our original rule of floor 4 being limited to Thursday or Friday. Now, let's look at what it means for floor 4 to go on a day consecutive to that of floor 7. If floor 3 was on Wednesday, floor 7 was on Thursday, and floor 5 was on Friday, it would be impossible for floor 4 to go on a day consecutive to floor 7. This is because Rule #1 states that the two floors examined on a given day must be separated by at least one floor, so floor 4 cannot be on the same day as floor 3 or 5. This concept eliminates the possibility for floor 4 to go on Wednesday or Saturday, keeping (A) in line with our original rule.

In general, I find it easiest to approach rule replacement questions by going through each answer choice one at a time. Oftentimes, these answer choices require you to think about or diagram what exactly they mean. When you do so, you should be focused on trying to find a scenario that would diverge from the original rule. It is important to really dive into the application of the answer choices, because the wording can seem simple on the surface (ex. (A)'s use of consecutive days), but can be combined with other rules of the game to have different implications. The more you practice and the more thoroughly you are able to breakdown the rules and other questions in the game, the more the reasoning of these questions should become clear.

Does that make sense? Please let us know if you have any other questions and best of luck with your studies!