#20 - Global, Must be True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?f=232&p=88732)

The correct answer choice is (B)

The numerical distribution discussed in the setup indicates that M reviews more plays than J (2 vs 1), and thus answer choice (B) is correct.

Note that answer choices (C), (D), and (E) each involve O, which is the lone wild card in this setup (O is able to review 1, 2, or 3 plays). These answers are unlikely to correct in a Must Be True question.

[lilRio]

Hello Powerscore Staff,

The fourth rule had me stumped last night. #20 gives us a chance to ponder the rule more with some of the answer choices. Answer choice D and E lets us explore if it Must be True that "O" can only be used once. Essentially, to prove D and E wrong, we have to make sure that we CAN have "O" only once. That is where the fourth rule confuses me. I read the rule many times over and interpreted it that two students have the same exact plays that they watch. However, reading other's posts, I see that this interpretation is incorrect. So in #20, D and E do not have to be true, because "O" can be used only once? Below is my hypothetical. Is this a correct solution that would follow all the rules, including the fourth rule? Does this hypothetical disprove answer choices D and E?

S: J
T: K O M
U: M L

[KelseyWoods]

Hi lilRio!

That 4th rule might be a little tricky but you don't actually need it for this question. This question is much easier, however, if you use the students as your base, rather than the plays.

With an undefined Grouping game like this where they don't tell us the exact group sizes, we need to think about how the rules restrict group sizes. Every student has to review at least one play. Since J and L and J and M cannot have any plays in common, that means that none of those 3 students can review all 3 plays because anyone who reviews all 3 plays has to have at least 1 play in common with everyone else. So the most that J, L, and M can have is 2 out of the 3 plays. The first rule tells us that K and L review fewer plays than M. That means that M can no longer review just 1 play. So M must review exactly 2 plays. Since M is reviewing exactly 2 plays, K and L must review exactly 1 play. J also has to review exactly 1 play because if J reviewed 2 plays it would have to have a play in common with M. Thus, we know that J, K, and L each review exactly 1 play, M reviews exactly 2 plays, which only leaves O who could review 1, 2, or 3 plays.

Here's what the setup ends up looking like:

Screen Shot 2020-10-07 at 4.38.18 PM.png

With that setup and those inferences regarding group sizes for each of our students, it is very clear that M must review more plays than J reviews.

Hope this helps!

Best,
Kelsey

[lilRio]

Dear Kelsey,

Thank you for your response. I appreciate your set up with the students as the base. Does rule #4 allow us to have the below hypothetical?:

S: J
T: K O M
U: M L

If so, then rule #4 does allow us to have a rule-abiding hypothetical that does not have two students with the exact same plays watched. In other words, rule #4 is still valid in this hypothetical because "U" has two students reviewing it. Is that right? Thank you for your consideration.

[Jeremy Press]

Hi lilRio,

Your hypothetical is permitted, both by Rule 4 and by all the other rules in the game. In your hypothetical, the exactly two students who are reviewing exactly the same play/plays as each other are K (who only reviews play T), and O (who also only reviews play T). M is not reviewing exactly the same plays as K and O, because M is reviewing play T and play U. Whereas student L is only reviewing play U. So that means M and L are not reviewing the exact same plays as each other (or as anyone else).

And you're correct that this hypothetical disproves answer choices D and E.

I just want to point out that what Kelsey is trying to show is that the inference this question is testing is something you can see directly (without going through a process of elimination) by using the students as the base of the game.

[lilRio]

Jeremy,

Thank you for your reply. I appreciate everyone's assistance on this question.