This is an explanation of the third logic game from Section IV of LSAT Preptest 75, the June 2015 LSAT.
Seven librarians, namely Flynn, Gomez, Hill, Kitson, Leung, Moore, and Zahn (F, G, H, K, L, M, Z) will be on duty from Monday through Saturday (M, T, W, Th, F, S). There will be one librarian on duty each day except on Saturday which will have two librarians. You must determined who can be on duty based on the rules.
This is a sequencing game. It has a slight twist in that two librarians are on Saturday. Otherwise, it’s exactly like pure sequencing games.
On these games, the optimal strategy is to combine all the rules into a large diagram. The only other difference on this game is that the final rule splits the game into two diagrams.
On this type of game the optimal strategy is to just draw the rules one by one and grow the diagram:
Rule 5 is the only tricky rule. It says that either L is before F, or L is on Saturday. So on the existing diagram we can just give L an “s” subscript to show it’s on Saturday if it’s after F:
Note that, without this rule, L could have been before F. L is after H, but H isn’t connected to F. So we could have put both H and L before or after F. Even now, we can still put H before F.
So, technically we should draw a line from F to L to show that F is before L. However, for me that makes the diagram more confusing. Personally I have no trouble remembering that in this diagram, H could be before or after F (even first!) but L must be on Saturday.
For the second diagram, draw everything else in the same order but place H and L before F:
That covers all possibilities. The rest is just reading the diagrams correctly. Remember, two librarians have a relationship only if lines connect them from left to right.
For instance, in the second diagram, we know nothing about the order or Z and M. Either could go before the other. Those two variables have no lines connecting them, so we have no idea which order they go in. The fact that Z is drawn to the right of M doesn’t mean anything – it’s the lines that matter.
On individual questions, I drew a diagram like this. But there’s nothing you can put in it for now:
Note that on my own page, I left off the days of the week. For me it’s easy to see which day is which, because I’ve previously drawn many games that use the days of the week. And it’s faster and smaller to draw diagrams without the days. I recommend you try it. I only drew them here in this explanation for clarity.
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