LSAT PrepTest 60 Logic Game #1 Explanation

The June 2010 LSAT (PrepTest 60) LSAT Logic Games section seems to have given enough people trouble that it makes sense for me to publish complete explanations for each of the 4 Logic Games in the section.

Don't look at these explanations until you've taken PrepTest 60 as a full-length timed exam.

This blog post covers the first Logic Game.

Also see:

PrepTest 60 (June 2010 LSAT), Game 2 Explanation
PrepTest 60 (June 2010 LSAT), Game 3 Explanation
PrepTest 60 (June 2010 LSAT), Game 4 Explanation

Explanations for Recent LSAT Logic Games

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Here's the main diagram:










Explanation of main diagram:

I've placed J and R to the right of the morning and afternoon rows, respectively, because they will have to go in those rows.

I've drawn K and N with slashes through them under the Wednesday column because they can never go on Wednesday (since Q must always occur at least one day prior to them).

I've drawn Q with a slash through it under the Friday column because it can never go on Friday (since both K and N must always occur at least one day prior to it).


Question 1:

Each of the incorrect choices will violate at least one rule.

Choice E has J in afternoon.
Choice D has R in morning.
Choice A has K before Q.
Choice C has Q and N on same day.

By elimination, the answer is B.


Question 2:

This sort of question can take forever if you start by testing each choice.

Looking at the rules, start by thinking about Q, K, and N, because they are involved in the rule that Q is before both K and N, and each of them is also involved in one of the other two rules.

Out of these 3 variables, Q is unique because it must go before the other two variables, so start by testing out Q on Thursday morning.

(N is unique also, because it's involved in the R rule, but Q trumps it because Q must go before 2 other variables, which give it unique restrictions regarding how late it can appear on the diagram.)

If Q on Thursday morning, then K and N would both have to be on Friday. J must be in the morning on the same day as either K or Q. If Q's already in the morning, it can't be with J. If K and N are both on Friday, then N can't be with J. As such, Q on Thursday morning violates the rule that J must be with either Q or K, and D is the answer.


Question 3:

We know that neither K nor N can ever be on Wednesday at all, so any choice containing at least one of the two is the answer.

Choice A contains K, so it's the answer.


Question 4:

If K's on Friday morning, this means J and Q must be on the same day with J in the morning. This creates two main possibilities. One with J and Q on Thursday and another with J and Q on Wednesday:
















J on Thursday morning occurs in the 1st of these 2 diagrams, so it's our answer, choice A.


Question 5:

We already know Q can't be on Thursday or Friday morning, so if it's to be on a morning, it must be on Wednesday morning.

This means J and K must be on the same day with J in the morning. This creates two main possibilities:
















Looking across these diagrams, we see J, K, N, and R appearing on Thursday, so we can eliminate all of those choices.

Whatever's left is our answer (choice E).


Question 6:

From previous diagrams, we've seen J, S, and Q appear on Wednesday morning, so choices A and B can be eliminated.

Out of the remaining variables, neither K nor N can be on Wednesday at all, and R is always in the afternoon, so it can't be on Wednesday morning either. That means J, S, and Q are the only ones who can appear on Wednesday morning, so the answer is 3 (choice C).

Photo by Urban Woodswalker